Intermediates to carbocyclic nucleosides

ABSTRACT

The present invention relates to certain purine nucleoside analogues containing a carbocyclic ring ill place of trip sugar residue, salts, esters and pharmaceutically acceptable derivatives thereof, processes for there preparation, pharmaceutical formulations containing them, and to the use of such compounds in therapy, particularly the treatment of or prophylaxis of certain viral infections.

This is a divisional of application Ser. No. 08/295,656, filed Sep. 12,1994 now U.S. Pat No. 5,641,884, which is a § 371 of PCT/GB93/00378,filed Feb. 24, 1993.

The present invention relates to purine nuclieoside analogues containinga carbocyclic ring in place of the sugar residue, pharmaceuticallyacceptable derivatives thereof, and their use in medical therapy,particularly for the treatment of certain viral infections.

Hepatitis B virus (HBV) is a small DNA containing virus which infectshumans. It is a member of the class of closely related viruses known asthe hepadnaviruses, each member of which selectively infects eithermammalian or avian hosts, such as the woodchuck and the duck.

Worldwide, HBV is a viral pathogen of major consequence. It is mostcommon in Asian countries, and prevalent in sub-Saharan Africa. Thevirus is etiologically associated with primary hepatocellular carcinomaand is thought to cause 80% of the world's liver cancer. In the UnitedStates more than ten thousand people are hospitalized for HBV illnesseach year, an average of 250 die with fulminant disease.

The United States currently contains an estimated pool of 500,000-1million infectious carriers Chronic active hepatitis will develop inover 25% of carriers, and often progresses to cirrhosis. It is estimatedthat 5000 people die from HBV-related cirrhosis each year in the USA,and that perhaps 1000die from HBV-related liver cancer. Even when auniversal HBV vaccine is in place, the need for effective anti-HBVcompounds will continue. The large reservoir of persistently infectedcarriers, estimated at 220 million worldwide, will receive no benefitfrom vaccination and will continue at high risk for HBV-induced liverdisease. This carrier population serves as the source of infection ofsusceptible individuals perpetuating the instance of diseaseparticularly in endemic areas or high risk groups such as IV drugabusers and homosexuals. Thus. there is a great need for effectiveantiviral agents, both to control the chronic infection and reduceprogression to hepatocellular carcinoma.

Clinical effects of infection with HBV range from headache, fever,malaise, nausea, vomiting, anorexia and abdominal pains. Replication ofthe virus is usually controlled by the immune response, with a course ofrecovery lasting weeks or months in humans, but infection may be moresevere leading to persistent chronic liver disease as outlined above. In"Viral Infections of Humans" (second edition, Ed., Evans, A.S. (1982)Plenum Publishing Corporation, N.Y.), Chapter 12 describes in detail theetiology of viral hepatitis infections.

Of the DNA viruses, the herpes group is the source of many common viralillnesses in man. The group includes cytomegalovirus (CMV), Epstein-Barrvirus (EEV), variceila zoster virus (VZV), herpes simplex virus (HSV)and human herpes virus 6 (HHV6).

In common with other herpes viruses, infection with CMV leads to alife-long association of virus and host and, following a primaryinfection, virus may be shed for a number of years- Clinical effectsrange from death and gross disease (microcephaly, hepatospienemegaly,jaundice, mental retardation) through failure to thrive, susceptibilityto chest and ear infections to a lack of any obvious ill effect. CMVinfection in AIDS patients is a predominant cause of morbidity as, in 40to 80% of the adult population, it is present in a latent form and canbe reactivated in immunocompromised patients.

EBV causes infectious mononucleosis and is also suggested as thecausative agent of nasopharyngeal cancer, immunoblastic lymphoma,Burkitt's lymphoma and hairy leukopiakia.

VZV causes chicken pox and shingles. Chicken pox is the primary diseaseproduced in a host without immunity. In young children, it is usually amild illness characterized by a vesicular rash and fever. Shingles isthe recurrent form of the disease which occurs in adults who werepreviously infected with varicella. The clinical manifestations ofshingles include neuralgia and a vesicular skin rash that is unilateraland dermatomal in distribution. Spread of inflammation may lead toparalysis or convulsions and coma can occur if the meninges becomesaffected. In immunodeficient patients, VZV may disseminate causingserious or even fatal illness.

HSV 1 and HSV 2 are some of the most common infectious agents of man.Most of these viruses are able to persist in the host's neural cells.Once infected, individuals are at risk of recurrent clinicalmanifestation of infection which can be both physically andpsychologically distressing. HSV infection is often characterized byextensive lesions of the skin, mouth and or genitals. Primary infectionsmay be sub clinical although they tend to be more severe than infectionsin individuals previously exposed to the virus. Ocular infections by HSVcan lead to keratitis or cataracts. Infection in the newborn, inimmunocompromised patients or penetration of infection into the centralnervous system can prove fatal. HHV6 is the causative agent of roseolainfantum (exanthum subitum) in children which is characterized by feverand the appearance of a rash after-the fever has declined. HHV6 has alsobeen implicated in syndromes of fever and/or rash and pneumonia orhapatitis in immunocompromised patients.

It has been reported that the carbocyclic analogue of 2'-deoxyguanosine(2'-CDG) i.e. (1 R*,3S*,4R*-2-amino-1,9-dihydro-g9- 3-hydroxy-4(hydroxymethyl)cyclopentyll!-6H-purine-6-one, is active against severalviruses. Thus in Proc. Natl. Acad. Sci. USA 1989, Vol. 86, pp8541-8544,it is disclosed that 2'-CDG inhibits hepatitis a viral replication. J.Med. Chem (1987) 30, pp746-749 and Biochemical Pharmacology (1 990) Vol.40, No. 7, ppl 1515-1522, report 2'-CDG, especially the (+)-enantiomer,as active against herpes simplex virus type 1 (HSV-1). Furthermore2'-CDG and general analogues thereof are disclosed together with aplurality of other compounds in the following patent publications: U.S.Pat. No. 4,543,255 (with reference to HSVI and 2), PCT 90/06671 (withreference to hepatitis B), EP 219838, PCT 91/13549 (with reference tocytomegalovirus (CMV)). Other publication relating to 2'-CDG and thepreparation thereof are J .Med. Chem. (1984) 27, pp1416-1421, and J.Chem. Soc. Chem. Commun. (1987) pp1083-1084.

It has now been discovered that certain analogues of 2'-CDG as referredto below, are useful for the treatment or prophylaxis of certain viralinfections According to a first aspect of the present invention, novelcompounds of the formula (I) are provided. ##STR1## wherein R¹represents hydrogen;

C₃₋₈ alkenyloxy; C₃₋₈ cycloalkoxy (e.g. cyclopentoxy); C₄₋₈cycloalkenyloxy (e.g. cyclopenten-3-yloxy); aryloxy (e.g. phenoxy) orarylalkoxy (e.g. benzyloxy) in which the aryl may be substituted withone or more C₁₋₄ kyl, halogen, hydroxy, C₁₋₄ alkoxy, amino or nitro;

C₃₋₆.alkenylthio (e.g. arlylthio); C₃₋₆ cydoalkylthio; C₄₋₈cycloalkenylthio; arylithio (e.g. phenylthio) or arylalkylthio (e.g.benzylthio) in which the aryl may be substituted with one or more C₁₋₄alkyl, halogen, hydroxy, C₁₋₄ alkoxy, amino or nitro;

an amino group, -NR² R³, in which R² and R³ may be the same or differentand are independently selected from hydrogen; C₁₋₈ alkyl; C₁₋₆ alkoxy;C₁₋₆ -hydroxyalkyl (e.g. hydroxyethyl); C₁₋₆ alkoxyalkyl (e.g.methoxyethyl); C₃₋₇ cycloalkyl (e.g cyclopropyl, cyclobutyl orcyclopentyl) in which the cycloalkyi may be substituted by one or moreC₁₋₆ alkyl or hydroxy; aryl (eg phenyl) or aralkyl (e.g. benzyl) inwhich the aryl may be substituted with one or more C₁₋₄ alkyl, halogen,hydroxy, C₁₋₄ alkoxy, amino or nitro; C₃₋₆ alkenyl (e.g. allyl); or R²and R³ together form a 4-to 8-membered ring (e.g. azetidinyl orpyrrolidinyl); provided that R² and R³ cannot both be hydrogen or bothbe C₁₋₈ atkyl;

4-morpholinyl, 1-piperazinyl or 1-pyrrollyl;

or a pharmaceutically acceptable derivative thereof.

It is to be understood that the present invention encompasses theparticular enantiomers depicted in formula (I), including tautomers ofthe purine, alone and in combination with their mirror-image enantiomerswhich are not depicted. Enantiomers depicted by formula (I), the"relevant" enantiomers, are preferred and more preferably the relevantenantiomer is provided substantially free of the correspondingenantiomer to the extent that it is generally in admixture with lessthan 10% w/w, preferably less than 5% w/w, more preferably less than 2%w/w and most preferably less than 1% w/w of the corresponding enantiomerbased on the total weight of the mixture.

However, the processes disclosed pertain to the preparation oppositeenantiomers via Examples 11-17 and Example 34.

Where reference herein is made to an alkyl moiety, this includes methyl,ethyl n-propyl, isopropyl, n-butyl, iso-butyl, tert-butyl, n-pentyl,iso-pentyl, neopentyl and hexyl.

Furthermore reference to C₃₋₇ cycloalkyl includes cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl.

Preferably R¹ represents a C₃₋₇ cycloalkylamino most preferablycyclopropyl.

Particularly preferred examples of compounds of formula (I), exhibitingdecreased toxicity compared to 2'-CDG, are:

a) (+)-(1S,2R,4R)-4-(2-amino-6(cyclopropylamino)-9H-purin-9-yl)-2-(hydroxymethyl)-1-cydcopentanol

b) (+)-(1S,2R,4S)-4-(2-amino-6-(cyclopropylmethylamino)-9H-purin-9yl)-2-(hydroxymethyl)-1cydopentanol

c)(+)-(1S,2R,4R)-4(2-amino-6(1-pyrrolidinyl)-9H-purin-9-yl)-2-(hydroxymethyl)-1-cyclopentanol

d) (+)-(1S,2R,4R) 46-allylthio)-2-amino-9H-purin-9-yl!-2-(hydroxymethyl)-1-cyclopentanol

e) (+)-(1S,2R,4R)-4.(2-amino-6-(cyclopentyloxy)-9H-purin-9-yl)-2-(hydroxymethyl)-1-cyclopentanol

f) (+)-(1S, 2R,4R)4(2-amino6-( 1-azetidinyl)-9H-purin-9-yl)-2-(hydroxymethyl)-1-cyclopentanol

and pharmaceutically acceptable salts thereof.

The compounds of formula (I) above and their pharmaceutically acceptablederivatives are herein referred to as the compounds according to theinvention.

In a further aspect of the invention there are provided the compoundsaccording to the invention for use in medical therapy particularly forthe treatment or prophylaxis of viral infections such as hepadnaviralinfections and herpes viral infections. To date compounds of theinvention has been shown to be active against hepatitis B virus (HBV)and cytomegalovirus (CMV) infections, although early results alsosuggest that the invention could also be active against other herpesvirus infections such as EBV, VZV, HSVI and II and HHV6.

Other viral conditions which may be treated in accordance with theinvention have been discussed in the introduction hereinbefore.

In yet a further aspect of the present invention there is provided:

a) A method for the treatment or prophylaxis of a hepadnaviral infectionsuch as hepatitis B or a herpes viral infection such as CMV whichcomprises treating the subject with a therapeutically effective amountof a compound according to the invention.

b) Use of a compound according to the invention in the manufacture of amedicament for the treatment prophylaxis of any of the above-mentionedinfections or conditions.

By "a pharmaceutically acceptable derivative" is meant anypharmaceutically or pharmacologically acceptable salt, ester or salt ofsuch ester of a compound according to the invention, or any compoundwhich, upon administration to the recipient, is capable of providing(directly or indirectly) a compound according to the invention, or anantivirally active metabolite or residue thereof.

Preferred esters of the compounds of the invention include carboxylicacid esters in which the non-carbonyl moiety of the ester grouping isselected from straight or branched chain alkyl, e.g. n-propyl, t-butyl,n-butyl, alkoxyalkyl (e.g-methoxymethyl), aralkyl (e.g. benzyl),aryloxyalkyl (e.g phenoxymethyl), aryl (e.g. phenyl optionallysubstituted by haloqen, C₁₋₄ alkyl or C₁₋₄ alkoxy or amino), sulfonateesters such as alkyl-or aralkyisulfonyl (e-g. methanesulfonyl); aminoacid esters (e.g. L-valyl or L-isoleucyl); and mono-, di- ortriphosphate esters. The phosphate esters may be further esterified by,for example, a C₁₋₂₀ alcohol or reactive derivative thereof, or by a2,3-di(C₆₋₂₄)acyl glycerol.

With regard to the above-described esters, unless otherwise specified,any alkyl moiety present advantageously contains 1 to 18 carbon atoms,particularly 3 to 6 carbon atoms such as the pentanoate. Any aryl moietypresent in such esters advantageously comprises a phenyl group.

Any reference to any of the above compounds also includes a reference toa pharmaceutically acceptable salt thereof.

Pharmaceutically acceptable salts include salts of organic carboxylicacids such as acetic, lactic. tartaric, malic, isethionic, lactobionic,p-aminobenzoic and succinic adds; organic sulfonic acids such asmethanesulfonic, ethanesulfonic, benzenesulfonic and p-toluenesulfonicacids and inorganic acids such as hydrochloric, sulfuric, phosphoric andsulfamic acids.

The above compounds according to the invention and theirpharmaceutically acceptable derivatives may be employed in combinationwith other therapeutic agents for the treatment of the above infectionsor conditions. Examples of such further therapeutic agents includeagents that are effective for the treatment of viral infections orassociated conditions such as acyclic nucleosides (e.g. acyclovir),immunomodulatory agents such as thymosin, ribonucleotide reductaseinhibitors such as 2-acetylpyridine 5-(2-chioroanilino)thiocarbonyl)thiocarbonohydrazone, interferons such asα-interferon, 1-β-D-arabinofuranosyl-5-(1-propynyl)uracil,3'-azido-3'-deoxythymidine, ribavirin and phosphonoformic acid. Thecomponent compounds of such combination therapy may be administeredsimultaneously, in either separate or combined formulations, or atdifferent times, e.g. sequentially such that a combined effect isachieved.

The compounds according to the invention, also referred to herein as theactive ingredient, may be administered for therapy by any suitable routeincluding oral, rectal, nasal, topical (including transdermal, buccaland sublingual), vaginal and parenteral (including subcutaneous,intramuscular, intravenous and intradermal). It will be appreciated thatthe preferred route will vary with the condition and age of therecipient, the nature of the infection and the chosen active ingredient.

In general a suitable dose for each of the above-mentioned conditionswill be in the range of 0.01 to 250 mg per kilogram body weight of therecipient (e.g. a human) per day, preferably in the range of 0.1 to100mg per kilogram body weight per day and most preferably in the range1.0 to 20 mg per kilogram body weight per day. (Unless otherwiseindicated, all weights of active ingredient are calculated as the parentcompound of formula (I); for salts or esters thereof, the weights wouldbe increased proportionally.) The desired dose is preferably presentedas two, three, four, five, six or more sub-doses administered atappropriate intervals throughout the day. These sub-doses may beadministered in unit dosage forms, for example, containing 10to 1000 mg,preferably 20 to 500 mg, and most preferably 100 to 400 mg of activeingredient per unit dosage form.

Ideally, the active ingredient should be administered to achieve peakplasma concentrations of the active compound of from about 0.025 toabout 100 μM, preferably about 0.1 to 70 μM, most preferably about 0.25to 50 μM. This may be achieved, for example, by the intravenousinjection of a 0.1 to 5% solution of the active ingredient, optionallyin saline, or orally administered as a bolus containing about 0.1 toabout 250 mg/kg of the active ingredient Desirable blood levels may bemaintained by a continuous infusion to provide about 0.01to about 5.0mg/kg/hour or by intermittent infusions containing about 0.4 to about 15mg/kg of the active ingredient.

While it is possible for the active ingredient to be administered aloneit is preferable to present it as a pharmaceutical formulation. Theformulations of the present invention comprise at least one activeingredient, as defined above, together with one or more acceptablecarriers thereof and optionally other therapeutic agents. Each carriermust be "acceptable" in the sense of being compatible with the otheringredients of the formulation and not injurious to the patient.Formulations include those suitable for oral, rectal, nasal, topical(including transdermal buccal and sublingual), vaginal or parenteral(including subcutaneous, intramuscular, intravenous and intradermal)administration. The formulations may conveniently be presented in unitdosage form and may be prepared by any methods well known in the art ofpharmacy. Such methods include the step of bringing into association theactive ingredient with the carrier which constitutes one or moreaccessory ingredients. In general, the formulations are prepared byuniformly and intimately bringing into association the active ingredientwith liquid carriers or finely divided solid carriers or both, and thenif necessary shaping the product

Compositions suitable for transdermal administration may be presented asdiscrete patches adapted to remain in intimate contact with theepidermis of the recipient for a prolonged period of time. Such patchessuitably contain the active compound 1) in an optionally buffered,aqueous solution or 2) dissolved and or dispersed in an adhesive or 3)dispersed in a polymer. A suitable concentration of the active compoundis about 1% to 25%. preferably about 3% to 15%-As one particularpossibility, the active compound may be delivered from the patch byelectrotransport or iontophoresis as generally described inPharmaceutical Research, 3 (6), 318 (1986).

Formulations of the present invention suitable for oral administrationmay be presented as discrete units such as capsules, cachets or tabletseach containing a predetermined amount of the active ingredient, as apowder or granules, as a solution or a suspension in an aqueous ornon-aqueous liquid; or as an oil-in-water liquid emulsion or awater-in-oil liquid emulsion. The active ingredient may also bepresented as a bolus, electuary or paste.

A tablet may be made by compression or molding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared bycompressing in a suitable machine the active ingredient in afree-flowing form such as a powder or granules, optionally mixed with abinder (e.g. povidone, gelatin, hydroxypropylmethyl cellulose),lubricant, inert diluent, preservative, disintegrant (e.g. sodium starchglycollate, cross-linked povidone, cross-linked sodium carboxymethylcellulose) surface-active or dispersing agent Molded tablets may be madeby molding in a suitable machine a mixture of the powdered compoundmoistened with an inert liquid diluent. The tablets may optionally becoated or scored and may be formulated so as to provide slow orcontrolled release of the active ingredient therein using, for example,hydroxypropyimethyl cellulose in varying proportions to provide thedesired release profile. Tablets may optionally be provided with anenteric coating, to provide release in parts of the gut other than thestomach.

Formulations suitable for topical administration in the mouth includelozenges comprising the active ingredient in a flavored basis, usuallysucrose and acacia or tragacanth; pastilles comprising the activeingredient in an inert basis such as gelatin and glycerin, or sucroseand acacia; and mouthwashes comprising the active ingredient in asuitable liquid carrier.

Formulations for rectal administration may be presented as a suppositorywith a suitable base comprising for example cocoa butter or asalicylate.

Formulations suitable for vaginal administration may be presented aspessaries, tampons, creams, gels, pastes, foams or spray formulationscontaining in addition to the active ingredient such carriers as areknown in the art to be appropriate.

Formulations suitable for parenteral administration include aqueous andnon-aqueous isotonic sterile injection solutions which may containanti-oxidants, buffers, bacteriostats and solutes which render theformulation isotonic with the blood of the intended recipient; andaqueous and non-aqueous sterile suspensions which may include suspendingagents and thickening agents-The formulations may be presented inunit-dose or multidose sealed containers, for example, ampules andvials, and may be stored in a freeze-dried (lyophilized) conditionrequiring only the addition of the sterile liquid carrier, for examplewater for injections, immediately prior to use. Extemporaneous injectionsolutions and suspensions may be prepared from sterile powders, granulesand tablets of the kind previously described.

Preferred unit dosage formulations are those containing a daily dose orunit, daily sub-dose, as herein above recited, or an appropriatefraction thereof, of an active ingredient.

It should be understood that in addition to the ingredients particularlymentioned above the formulations of this invention may include otheragents conventional in the art having regard to the type of formulationin question, for example, those suitable far oral administration mayinclude such further agents as sweeteners, thickeners and flavoringagents.

The present invention further includes the following process for thepreparation of compounds of formula (1) above and derivatives thereofeither alone or in combination with their corresponding enantiomers. Theprocess according to the present invention comprises treating a compoundof formula (Ia) either alone or in combination with its enantiomer(wherein Z represents a precursor group for the said R¹ group, R¹defined as in formula (I)). ##STR2##

The conversion of (Ia) to (I) may be carried out in a conventionalmanner, for example, by treatment of a compound of formula (Ia) in whichZ represents a leaving group (e.g. a halo such as a chloro group) withan appropriate amine (e.g. methylamine or dimethylamine) or anappropriate alkoxide (e.g. sodium methoxide or potassium n-butoxide) oran appropriate alkylsulfide. (e.g. sodium methylmercaptide) or withsodium hydrogen sulfide or thiourea to provide the 6-thiopurine (R¹=mercapto) which is then alkylated with appropriate alkylating agents(e.g. n-propyl iodide, allyl chloride, and dimethyl sulfate) in thepresence of an equivalent of base (e.g. sodium hydroxide or potassiumt-butoxide) to provide the corresponding alkylthio compounds of formula(I).

The compounds of formula (Ia) employed as starting materials in theabove process may be prepared by reacting a compound of formula (II)either alone or in combination with its enantiomer(wherein Z is definedas in formula (Ia) and R⁴ and R⁵ are either the same or different andmay be either hydrogen, formyl, or an amino protecting group such as aC₂₋₆ alkanoyl, e.g. acetyl or isobutyryl, or C₁₋₆ alkoxycarbonyl, e.g.tert-butoxycarbonyl) with a reactive derivative of formic acid (e.g.triethylorthoformate or diethoxymethyl acetate) optionally with acosolvent such as dimethylacetamide or dimethylformamide. ##STR3##

It is understood that when R⁵ is other than hydrogen or formyl,deprotection preferably by prior treatment with dilute aqueous mineralacid is required prior to treatment with a reactive derivative of formicacid. In these cases the resulting mineral acid salt of (II) with R⁴ andR⁵ being hydrogen is efficiently converted directly to compounds offormula (Ia) by treatment with derivatives of formic acid, e.g.triethylorthoformate, preferably at 25° C. for several hours When othercompounds of formula (II) are reacted with derivatives of formic acid,the reaction is conveniently effected by the addition of slightly morethan one equivalent of a strong anhydrous acid, e.g. with 1.1equivalents of ethanesulfonic acid per equivalent of (II) or 4equivalents of concentrated aqueous hydrochloric acid per equivalent of(II), preferably at 25° C. It is understood that subsequent treatment ofthe resulting products with dilute aqueous acid, e.g. 1 N hydrochloricacid at 25°°C. for several hours cleaves derivatives formed, forexample, by reaction of the hydroxy groups with triethylortho-formate.

The compounds of formula (II) employed as starting materials in theabove process may be prepared by reacting a compound of formula (IIIa)either alone or in combination with its enantiomer with an appropriatelysubstituted pyrimidine, e.g. 2,5-diamino-4,6-dichloropyrimidine orpreferably derivatives thereof, e.g.,N(4,6-dichloro-5-formamido-2-pyrimidinyl) isobutyramide as described inEP 434450, Jun. 26, 1991. This reaction is preferably carried out at80°-120° C., e.g. at reflux in n-butanol or t-butanol with 1-2equivalents of a base, e.g. triethylamine or potassium carbonate, for 1to 3 hours. ##STR4##

The compounds of formula (IIIa), either alone or in combination withtheir enantiomers. employed as starting materials as described above maybe prepared for example by deprotection of protected compounds offormula (IIIb) by methods known in the art (T. W. Greene, "ProtectiveGroups in Organic Synthesis," Wiley, N.Y., 1981, pp 218-287; J. F. W.McOmie, "Protective Groups in Organic Chemistry" Plenum Press, N.Y.,1973, pp 43-93)

Most preferably, when R⁶ =tert-butoxycarbonyl (BOC), deprotection can beachieved by the reaction with an acid of pKa less than three as is knownin the art and is exemplified below. The amino diol of structure (IIIa)is so obtained in the form of its salt, which is suitable for use in thereaction to prepare compounds of formula (I). The free base of the aminodiol (IIIa) is obtained, for example, by contacting the salt with aquaternary ammonium-type anion exchange resin in its hydroxide form asis exemplified below.

The compounds of formula (IIIb) employed as starting materials asdescribed above may be prepared for example by desilylation of protectedcompounds of formula (IVa) by reaction with fluoride ion, as is known inthe art and exemplified below (T. W. Greene, "Protective Groups inOrganic Synthesis, " Wiley, N.Y., 1981, pp 218-287; J. F. W. McOmie,"Protective Groups in Organic Chemistry," Plenum Press, N.Y., 1973, pp.43-93; W. T. Markiewicz, Tetrahedron Letters 1980, 21, 4523-4524); W. T.Markiewicz and M. Wiewiorowski, Nucleic Acids Research SpecialPublication No. 4, 3185-3188; W. T. Markiewicz, J. Chem. Research (S)1979, 24-25; C. H. M. Verdegaal, P. L. Jansse, J. F. M. deRooij, G.Veeneman and J. H. vanBoom, Recueil 1981,100, 200-204; C. Gioeli, M.Kwiatkowski, B. Oberg and J. B. Chattopadhyaya, Tetrahedron Letters 981,22 1741-1744). ##STR5##

It is surprising in view of the prior art that substantially less thantwo equivalents of fluoride ion is sufficient to effect deprotection. Inthe present case, approximately one equivalent of tetraethylammoniumfluoride was found to be sufficient.

The compounds of formula (IVa) employed as starting materials asdescribed above may be prepared for example by first thiocarbonation ofthe compounds of formuia (IVc) to prepare thiocarbonates of formula(IVb), then reduction of the thiocarbonates of formula (IVb) with e.g.tributyltin hydride as is known in the art (M. J. Robins and J. S.Wilson, J. Am. Chem. Soc. 1981, 103, 932-933; M. J. Robins, J. S. Wilsonand F. Hansske, J. Am. Chem. Soc. 1985, 105, 4059-4065; W. Hartwig,Tetrahedron 1983, 39, 2609-2645 and references therein; D. H. R. Barton,D. Crich, A. Lobberding and S. Z. Zard, Tetrahedron 1986, 42, 2329-2338;D. H. R. Barton and S. W. McCombie, J. Chem. Soc., Perkin I 1975,1574-1585; D. H. R. Barton, W. B. Motherwell and A. Stange, Synthesis1981,743-745; N. Katagiri, M. Nomura, M. Muto and C. Kaneko, Chem.Pharm. Bull. 1991, 39, 1682-1688) and is exemplified below.

The compounds of formula (IVc) employed as starting materials asdescribed above may be prepared for example by selective protectionthrough reaction of compounds of formula (V) with1,3-dichloro-1,1,3,3-tetraisopropyl disiloxane as is known in the art(W. T. Markiewicz, N. S. Padyukova, Z. Samek, J. Smrt, CollectionCzechoslov. Chem. Commun. 1980, 45, 1860-1865: W. T. Markiewicz,Tetrahedron Letters 1980, 21, 4523-4524; W. T. Markiewicz and M.Wiewiorowski, Nucleic Acids Research Special Publication No.4,3185-3188; W. T. Markiewicz, J. Chem. Research (S) 1979, 24-25; C. H.M. Verdegaal, P. L. Jansse, J. F. M. deRooij, G. Veeneman and J. H.vanBoom, Recueil 1981, 100, 200-204; C. Gioeli, M. Kwiatkowski, S. Obergand J. B. Chattopadhyaya, Tetrahedron Letters 1981, 22, 1741-1744) andis exemplified below. ##STR6##

The compounds of formula (V) employed as starting materials as describedabove may be prepared for example by cis-dihydroxylation of compounds ofstructure (VIIa) using a catalytic amount of osmium tetroxide andN-methyl morpholine-N-oxide as is known in the art (V. VanRheenen, R. C.Kelly and D. Y. Cha, Tetrahedron Letters 1976, 1973-1976; M. Schroder,Chem. Rev. 1980, 80, 187-213). The cis-hydroxylation reaction results ina mixture of two geometrical isomers of structure (VI) and (V). Theseparation of these isomers can be achieved by conventional methods suchas chromatography or selective crystallization. The isomers wherein R⁶is BOC are most easily separated by crystallization. as is exemplifiedbelow. ##STR7##

The compounds of formula (VIIa) employed as starting materials asdescribed. above may be prepared for example by protection of thecompound of formula (VIIb) by methods known in the art(T. W. Greene,"Protective Groups in Organic Synthesis," Wiley, N.Y., 1981,pp. 218-287;J. F. W-McOmie, "Protective Groups in Organic Chemistry," Pienarn Press,New York, 1973, pp. 43-93). Preferred are R⁶ =C₂₋₆ alkanoyl (e.g. acetyland C2-6 alkyloxycarbonyl (e.g. tert-butoxy carbonyl, BOC). Mostpreferred is R⁶ =BOC, which is exemplified below.

The resolved (-)-amino alcohol of formula (VIIb) or a protectedderivative (VIIa) can now be used to synthesize resolved carbocyclicnucleosides, (e.g. (1S, 4R)-4-(2-amino-6-(cyclopropylamino)-9H-purin-9yl)-2-cyclopentene-1-methanol) asillustrated in EP 434450 (U.S. Pat. No. 5,087,697) and in the exampleshereinafter. Thus, an enantiomer of a carbocyclic nucleoside isobtainable by applying reactions that form the corresponding pyrimidineor purine base of the desired nucleoside, as in known in the art andillustrated herein.

It will be appreciated that the steps from formation of the resolved(-)-amino alcohol of formula (VIIb) up to formation of (1S,4R)-(2-amino-6-(cyclopropylamino)-9H-purin-9-yl)-2-cyclopentene-1-methanolas described in EP 434450 (U.S. Pat. No. 5,087,697) are incorporatedherein by reference, in particular Examples 1-5, 15-19, 26-28 anddescribed herein (Examples 30-33)

Another aspect of the present invention includes a process for thepreparation of (-)-(1 S,4R)-4amino-2-cyclopentene-1-methanol, compound(VIIIb), its mirror image enantiomer and mixtures of such enantiomers.Each mirror image enantiomer can be used to prepare in conventionalmanner antiviral carbocyclic nucleosides of the correspondingenantiomeric configuration, for example as described in Molec. Pharm.37, 395-401 (1990) and J. Med. Chem. 30, 746-749 (1987). This processcomprises reducing (-)-(2S,4R)-4-amino-2-cyclopertene-1-carboxytic acid,compound (VIII), the mirror image enantiomer thereof or a mixture ofsuch enantiomers ##STR8##

It is preferred that compound (VIII) or its mirror image enantiomer bein the form of a salt, (VIIIa) or (VIIIb). Subsequent references to(VIII), (VIIIa) and (VIIIb) also include the mirror image enantiomersthereof and mixtures of the corresponding enantiomers. Suitable salts(VIIIa) include the lithium, sodium, potassium, magnesium or calciumsalts. Most preferred is the sodium salt (W=Na in structure (VIIIa)).Suitable salts (VIIIb) are those wherein the conjugate acid (XH) of thesalt posses a pKa less than two. Suitable salts (VIIIb) thus include thehydrochloride, sulphate, bisulphate, hydrobromide, or organic sulphonicacid salt.

It is further preferred that-the salt (VIIIb) be an organic sulphonicacid salt. It is most preferred that the organic sulphonic acid salt isa C₁₋₆ ; alkyl sulphonic acid salt (e.g. methanesulphonyl) or arylsulphonic acid salt (e.g. toluenesulphonyl). In structure (VIIIb), Xwould thus represent most preferably e.g. a methanesulphonate ortoluenesulphonate group, respectively.

The present invention also includes the novel compounds of formulas(VIIIa) and (VIIIb) generically and specifically referred to above

The reducing agent for conversion of (VIII), (VIIIa), or (VIIIb) to(VIIb) or for conversion of the respective mirror image enantiomers ispreferably an aluminum hydride, such as diisobutyl aluminum hydride,sodium bis (2-methoxyethoxy)aluminum hydride, lithium aluminum hydride,sodium aluminum hydride, lithium tri-tert-butoxyaluminohydride, etc.Most preferred is lithium aluminum hydride (D. A. Dickman, A. I. Meyers,G. A. Smith and R. E. Cawley, Org. Syn. Coll. Vol VII, 350-533).Advantageously a source of fluoride ion such as NaF (H. Yamamoto and K.Maruoka, J. Org. Chem. 191, 103, 4186-4194) is also used to help releasethe product from contaminating aluminum following the reductionreaction. Triethanolamine (J. Powell, N. James and S. J. Smith,Synthesis, 1986,338-340) can be used in place of fluoride, but is lesspreferred.

The solvent for the reduction reaction is preferably an ether such asTHF. It is further preferred that water(1-15% w/w) be added to the etherprior to isolation of the product, in order to increase the solubilityof(VIIb).

In yet a further aspect of the invention there is provided a method ofpreparing compound (VIIIb), its mirror image enantiomer or a mixture ofsuch enantiomers, comprising reacting (-)-2-azabicyclo2.2.1!hept-5-en-3-one (IX), its mirror image enantiomer a mixture ofsuch enantiomers, with one or more equivalents of an add and one or moreequivalents of water. Preferred acids are those with pKa less than two,most preferred are acids that give directly the salts (VIIIb) describedabove, e.g. including methanesulphonic add and toluenesulphonic acid.##STR9##

The reaction temperature can vary between 10° C. and 120° C., but ismost preferably between 30° C. and 70° C.

The choice of solvent for this hydrolysis reaction can be quite varied,ranging from water to hydrocarbon solvents. The preferred solvent is theone that will be used in the subsequent reduction step. in this case,intermediate (VIII or VIIIa or VIIIb) can be used directly, withoutisolation.

Compound (VIII) and the salts (VIIIa) are prepared from the salt (VIIIb)by contacting it with 3 base and isolating the product by precipitation,crystallization, evaporation, et as is known to those skilled in theart. Almost any base with pKa greater than 3.5 can be used to make(VIII). The salt (VIIIa) must be prepared by contacting (VIIIb) with abase containing (W+) For example, the sodium salt can be prepared bycontacting (VIIIb) with about two equivalents of the base sodiumhydroxide.

In the present invention, it is also possible to easily remove color andimpurities from the salt of intermediate (VIII) by washing it in thereactor (U.S. Pat. No. 4,734,194 Mar. 29, 1988)). Under the protocolexemplified hereinafter, the toluenesulphonate and methane-sulphonatesalts are found to be of particular advantage in that they filterexceptionally quickly.

As a further extension of the present invention, the sulphonic acid saltof compound (VIII), its mirror image enantiomer or a mixture of suchenantiomers, is prepared by performing an oxidative hydrolysis reactionon the Diels-Alder adduct between cyclopentadiene and an alkyl or arylsulphonyl cyanide (X). ##STR10## wherein R⁷ is C₁₋₆ alkyl or aryl, itsmirror image enantiomer or a mixture of such enantiomers. Preferred iswhere R⁷ is methyl, phenyl, or tolyl. Most preferred is tolyl.

The literature (J. C. Jagt and A. M. vanleusen, J. Org. Chem. 1974, 39,564-566) teaches that the Diels-Alder adduct (X) is a particularlyconvenient precursor to the lactam (IX) by a hydrolysis reaction. Thus,by the application of an oxidative hydrolysis reaction to Diels-Alderadduct (X), compound (VIIIb) in its further preferred form can beobtained directly, and a step is saved in the overall process to preparecompound (VIIIb).

The oxidative hydrolysis reaction is accomplished by contactingDiels-Aider adduct (X) with at least one equivalent of water, at leastone equivalent of an oxidizing agent, and preferably a catalytic amountof an acid.

The choice of solvent can be quite varied. It is preferable to use asolvent that poses a low hazard when combined with the oxidizing agent.Most preferred is to use water as both solvent and hydrolytic agent.

Suitable oxidizing agents are those that do not oxidize a double bond.Preferred are peroxides, most preferred is hydrogen peroxide. One tofive equivalents of the oxidizing agent can be used.

In the preferred embodiment where a catalytic amount of acid is used,any acid of pKa less than 3 can be used, but it is preferred that theacid used be the same as the salt of compound (VIIIb) that is formedfrom the Diels-Alder adduct (VIIIb). For example, if R=tolyl in theadduct(X), the oxidative hydrolysis gives-the toluenesulphonate salt ofcompound (VIIIb). In this case, toluenesulphonic acid would be thepreferred acid. If R=methyl in the adduct (X), the preferred acid wouldbe methanesulphonic acid, etc. The amount of acid catalyst can rangefrom 0 to 50 mol % relative to the Diels-Alder adduct (X).

All of the structures shown above are intended to represent the racematein addition to the single enantiomer depicted. Thus, the presentinvention is intended to encompass both the racemates and the pureenantiomers, substantially free of their mirror-image isomers.

A compound of formula (I) may be converted into a pharmaceuticallyacceptable ester by reaction with an appropriate esterifying agent, e.g.an acid halide or anhydride. The compound of formula (I) includingesters thereof, may be converted into pharmaceutically acceptable saltsthereof in conventional manner, e.g. by treatment with an appropriateacid An ester or salt of an ester of formula (I) may be converted intothe parent compound, e.g. by hydrolysis.

The following Examples are intended for illustration only and are notintended to limit the scope of the invention in any way. The term`active ingredient` as used in the examples means a compound of formula(I) or a pharmaceutically acceptable derivative thereof.

EXAMPLE A: Tablet Formulations

The following formulations A and B were prepared by wet granulation ofthe ingredients with a solution of povidone, followed by addition ofmagnesium stearate and compression

    ______________________________________                                        Formulation A                                                                                    mg/tablet                                                                              mg/tablet                                         ______________________________________                                        (a) Active ingredient                                                                            250      250                                               (b) Lactose B.P.   210      26                                                (c) Povidone B.P.  15       9                                                 (d) Sodium Starch Glycollate                                                                     20       12                                                (e) Magnesium Stearate                                                                           5        3                                                                    500      300                                               ______________________________________                                        Formulation B                                                                                    mg/tablet mg/tablet                                        ______________________________________                                        (a) Active ingredient                                                                            250       250                                              (b) Lactose        150       --                                               (c) Avicel PH 101  60        26                                               (d) Povidone B.P.  15        9                                                (e) Sodium Starch Glycollate                                                                     20        12                                               (f) Magnesium Stearate                                                                           5         3                                                                   500       300                                              ______________________________________                                        Formulation C                                                                                  mg/tablet                                                    ______________________________________                                        Active ingredient                                                                              100                                                          Lactose          200                                                          Starch           50                                                           Povidone         5                                                            Magnesium stearate                                                                             4                                                                             359                                                          ______________________________________                                    

The following formulations, D and E, were prepared by direct compressionof the admixed ingredients. The lactose used in formulation E was of thedirect compression type (Dairy Crest-"Zeoarox").

    ______________________________________                                                           mg/tablet                                                  ______________________________________                                        Formulation D                                                                 Active ingredient  250                                                        Pregelatinised Starch NF15                                                                       150                                                                           400                                                        Formulation E                                                                 Active Ingredient  250                                                        Lactose            150                                                        Avicel             100                                                                           500                                                        ______________________________________                                    

Formulation F (Controlled Release Formulation)

The formulation was prepared by wet granulation of the ingredients(below) with a solution of povidone followed by the addition ofmagnesium stearate and compression.

    ______________________________________                                                                   mg/tablet                                          ______________________________________                                        (a)      Active ingredient 500                                                (b)      Hydroxypropylmethylcellulose                                                                    112                                                         (Methocel K4M Premium)                                               (c)      Lactose B.P.      53                                                 (d)      Povidone B.P.C.   28                                                 (e)      Magnesium Stearate                                                                              7                                                                             700                                                ______________________________________                                    

EXAMPLE B: Capsule Formulations

Formulation A

A capsule formulation was prepared by admixing the ingredients ofFormulation D in Example 1 above and filling into a two-part hardgelatin capsule. Formulation B (infra) was prepared in a similar manner.

    ______________________________________                                                           mg/capsule                                                 ______________________________________                                        Formulation B                                                                 (a) Active ingredient                                                                            250                                                        (b) Lactose B.P.   143                                                        (c) Sodium Starch Glycollate                                                                      25                                                        (d) Magnesium Stearate                                                                            2                                                                            420                                                        Formulation C                                                                 (a) Active ingredient                                                                            250                                                        (b) Macrogol 4000 BP                                                                             350                                                                           600                                                        ______________________________________                                    

Capsules were prepared by melting the macrogol 4000 BP, dispersing theactive ingredient in the melt and filling the melt into a two-part hardgelatin capsule.

    ______________________________________                                        Formulation D                                                                                 mg/capsule                                                    ______________________________________                                        Active ingredient                                                                             250                                                           Lecithin        100                                                           Arachis Oil     100                                                                           450                                                           ______________________________________                                    

Capsules were prepared by dispersing the active ingredient in thelecithin and arachis oil and filling the dispersion into soft, elasticgelatin capsules.

Formulation E (Controlled Release Capsule)

The following controlled release capsule formulation was prepared byextruding ingredients a, b and c using an extruder, followed byspheronisation of the extrudate and drying. The dried pellets were thencoated with release-controlling membrane (d) and filled into atwo-piece, hard gelatin capsule.

    ______________________________________                                                           mg/capsule                                                 ______________________________________                                        (a) Active Ingredient                                                                            250                                                        (b) Microcrystalline Cellulose                                                                   125                                                        (c) Lactose BP     125                                                        (d) Ethyl Cellulose                                                                               13                                                                           513                                                        ______________________________________                                    

EXAMPLE C

Injectable Formulation

    ______________________________________                                        Formulation A.                                                                ______________________________________                                        Active ingredient     0.200 g                                                 Hydrochloric acid solution, 0.1M                                                                    q.s. to pH 4.0 to 7.0                                   Sodium hydroxide solution, 0.1M                                                                     q.s. to pH 4.0 to 7.0                                   Sterile water         q.s. to 10 ml                                           ______________________________________                                    

The active ingredient was dissolved in most of the water (35°-400°C) andthe pH adjusted to between 4.0 and 7.0 with the hydrochloric acid or thesodium hydroxide as appropriate. The batch was then made up to volumewith the water and filtered through a sterile micropore filter into asterile 10 ml amber glass vial (type 1) and sealed with sterile closuresand overseals.

    ______________________________________                                        Formulation B.                                                                ______________________________________                                        Active ingredient        0.125 g                                              Sterile, pyrogen-free, pH 7 phosphate buffer,                                                          q.s. to 25 ml                                        ______________________________________                                    

EXAMPLE D

    ______________________________________                                        Intramuscular injection                                                       ______________________________________                                        Active Ingredient    0.20 g                                                   Benzyl Alcohol       0.10 g                                                   Glycofurol           1.45 g                                                   Water for injection  q.s. to 3.00 ml                                          ______________________________________                                    

The active ingredient was dissolved in the glycofurol. The benzylalcohol was then added and dissolved, and water added to 3 ml. Themixture was then filtered through a sterile microcpore filter and sealedin sterile 3 ml amber glass vials (type 1).

EXAMPLE E

    ______________________________________                                        Syrup                                                                         ______________________________________                                        Active ingredient    0.2500 g                                                 Sorbitol Solution    1.5000 g                                                 Glycerol             2.0000 g                                                 Sodium Benzoate      0.0050 g                                                 Flavour, Peach 17.42.3169                                                                          0.0125 ml                                                Purified Water       q.s. to 5.0000 ml                                        ______________________________________                                    

The active ingredient was dissolved in a mixture of the glycerol andmost of the purified water. An aqueous solution of the sodium benzoatewas then added to the solution, followed by addition of the sorbitolsolution and finally the flavour. The volume was made up with purifiedwater and mixed well.

EXAMPLE F

    ______________________________________                                        Suppository                                                                                           mg/suppository                                        ______________________________________                                        Active Ingredient (63lm)*                                                                              250                                                  Hard Fat, BP (Witepsol H15 - Dynamit Nobel)                                                           1770                                                                          2020                                                  ______________________________________                                         *The active ingredient was used as a powder wherein at least 90% of the       particles were of 63lm diameter or less.                                 

One-fifth of the Witepsol H15 was melted in a steam-jacketed pan at 45°C. maximum. The active ingredient was sifted through a 200lm sieve andadded to the molten base with mixing, using a silverson fitted with acutting head, until a smooth dispersion was achieved. Maintaining themixture at 45° C. the remaining Witepsol H15 was added to the suspensionand stirred to ensure a homogeneous mix. The entire suspension waspassed through a 250lm stainless steel screen and, with continuousstirring, was allowed to cool to 40° C. At a temperature of 38° C. to40° C., 2.02 g of the mixture was filled into suitable, 2 ml plasticmoulds. The suppositories were allowed to cool to room temperature.

EXAMPLE G

    ______________________________________                                        Pessaries                                                                                       mg/pessary                                                  ______________________________________                                        Active ingredient (63lm)                                                                        250                                                         Anhydrate Dextrose                                                                              380                                                         Potato Starch     363                                                         Magnesium Stearate                                                                              7                                                                             1000                                                        ______________________________________                                    

The above ingredients were mixed directly and pessaries prepared bydirect compression of the resulting mixture.

Antiviral Testing

Human cytomegalovirus (HCMV) is assayed in monolayers of MRCS cells(human embryonic lung) in multiwell trays. Activity of compounds isdetermined in the plaque reduction assay, in which a cell monolayer isinfected with a suspension of HCMV. A range of concentrations of thecompound to be tested (of known molarity) is then incorporated into thecarboxymethyl cellulose overlay. Plaque numbers of each concentrationare expressed as percentage of the control and a dose-response curve isdrawn. From this curve the 50% inhibitory concentration (IC₅₀) isestimated.

    ______________________________________                                        Anti-HCMV Activity                                                                   Compound                                                                              IC.sub.50 (μM)                                              ______________________________________                                               Ex. 22  3.1                                                                   Ex. 23  2.8                                                            ______________________________________                                    

Toxicity Testing

Compounds of formula (I) were tested for toxicity in human bon marrowprogenitor cells, in vitro, by the method of Dornsife, R. E. et al.,1991, Antimicrob. Agents Chemother., 35: 322-328. Three separate assayswere performed using marrow from three different donors.

    ______________________________________                                        Cell Toxicity                                                                                 I.sub.50 (μM).sup.+                                        Compound        CFU-GM   BFU-E                                                ______________________________________                                        Ex.22           34 ± 14                                                                             >>50                                                 Ex. 23          14 ± 1                                                                              55 ± 15                                           2'-CDG          0.4 ± 0.3                                                                           4 ± 2                                             ______________________________________                                         .sup.+ 50% inhibition of bone marrow progenitor cells.                   

EXAMPLE 1

(-)-(1S, 4R)4-Amino-2-cyclopentene-1-carboxylic acid methanesulfonate

A solution of (-)-2-azabicyclo 2.2.1!hept-5-en-3-one (97.45 g, 0.8929mol, Enzymatix Ltd.) in tetrahydrofuran (500 mL) was filtered and warmedto 35° C. A solution of methanesulfonic add (63.7 mL, 0.9817 mol) inwater (24.1 ml, 1.34 mol) was added over the course of 1.5 hourssuch-that the ensuing exotherm did not exceed 45° C. The resultingslurry was heated at 60° C. for three hours, then allowed to cool toroom temperature over the course of 15 hours. The slurry was filteredand the cake washed twice with anhydrous tetrahydrofuran (200 mL). Ananalytical sample of the wet cake was removed and dried to give thetitle compound as a white solid (1.264 g); m.p. 167°-169.2°C.; ¹ H-NMR(DMSO-d₆)δ: 12.6 (br s, 1H, CO₂ H),8.04 (br s, 3H, NH₃ ⁺),6.10(dt,J=5.6, 2.0, 2.0 Hz, 1H, vinyl), 5.85(dt, J=5.3, 2.3, 2.3Hz, 1H,vinyl), 4.19(brs, w1/2=20Hz, 1H, allylic H), 3.61 (m, w1/2=22Hz, 1 H,allylic H), 2.53 (quintet, J=5.3 Hz (overlapping with DMSO peak),1/2CH₂), 2.39 (s, 3H, CH₃ SO₃ H), 1.93 (dt,J=6.7, 6.7, 13.7 Hz, 1H,1/2CH₂); α!²⁰ ₅₈₉ -83.8°, α!²⁰ ₅₇₈ -87.4°, α!²⁰ ₅₄₆ -101.2°, α!²⁰ ₄₃₆-186.7°, α!²⁰ ₃₆₅ -316.2°(c=1.42, methanol); Cl-MS(CH₄):128(M+1);El-MS:127(M).

Anal. Calcd. for C₇ H₁₃ NO₅ S: C, 37.66,H, 5.87: N, 6.27: S. 14.36.

Found: C, 37.65; H, 5.88;N, 6.30; S, 14.44.

The remaining wet cake was used directly in the following example.

EXAMPLE 2 (-)-(1S, 4R)-4-Amino-2-cvclopentene1-methanol

The tetrahydrofuran-wet cake of (-)-(1S,4R)4amino-2-cyclopetene-1-carboxylic acid methanesulfonate prepared inthe above example was suspended in dry tetrahydrofuran (400 mL) andtransferred via cannula to a rapidly stirring solution of lithiumaluminum hydride in tetrahydrofuran (1.0 molar, 1600 mL, 1.6 mol,Aldrich) cooled in an ice/acetone bath. The rate of transfer was limitedto control the rate of gas evolution and to keep the temperature between0° and 10° C. (total time of addition 1.5 hours)-The resulting mixturewas warmed to reflux over the course of two hours, then refluxed for 16hours.

Approximately 1.6 L of solvent was removed by distillation, theresulting slurry was cooled in an ice-acetone bath, then treated withdiethyl ether (dry, 1 L) and sodium fluoride (403.3 g, 9.605 mol,Aldrich). Water (86 mL, 4.8 mol) was added slowly at such a rate (threehours) that the temperature was kept below 5° C. and the hydrogenevolution was moderated. The resulting slurry was filtered and the cakewashed with tetrahydrofuran (200 mL), then 7% water-tetrahydrofuran (500mL). Quantitative HPLC analysis (see Example 3, below) of the filtrateshowed it to contain 60.04 g of the title compound. The cake wasreslurried in 7% water-tetrahydrofuran (1 L) for a half hour, filtered,and washed with 7% water-tetrahydrofuran (400 mL),then 10%water-tetrahydrofuran (300 mL). Quantitative HPLC analysis (see Example3, below) of the filtrate showed it to contain 26.70 g of the titlecompound. The cake was reslurried in methanol (1 L) for 16 hours,filtered, and washed with methanol (500 mL). Quantitative HPLC analysis(see Example 3, below) of the filtrate showed it to contain 4.09 g ofthe title compound. The total yield of the title compound was thus 90.83g, 0.8027 mol, or 90.5% of theoretical yield corrected for theanalytical sample removed.

EXAMPLE 3 Analysis of (-)-(1 S, 4R)-4-Amino-2-cyclopentene-1-methanoland its enantiomer, (+)-(1R, 4S)-4-amino-2-cyclopentene-1-methanol

Samples of the title compounds were characterized by the method ofBruckner, H., Wittner, R. and Godel, H., "Automated Enantioseparation ofAmino Acids by Derivatization with o-Phthaldialdehyde and N-AcylatedCysteines", J. Chrom., 476 (1989) 73-82. Using o-phthaldialdehyde andN-acetyl-L-cysteine as derivatizing reagents. The chromatographicseparation used an Optima II ODS 100×4.5 mm, 3 μm column (III SuppliesCo., Meriden, Conn.) and gradient elution at 0.9 mL/min using initially100% sodium acetate buffer, 40 mM, pH 6.5, with a linear ramp to 18%acetonitrile over 15 minutes and a subsequent hold at 18% acetonitrilefor 15 minutes. Detection was at 338 nm. Samples were dissolved in 0.1molar borate buffer, pH 10.4. The identity and purity of the samples wasestablished by comparison with authentic standards (see EP 434450 (Jun.26, 1991)). The retention time of the (1S, RS) isomer was about 21minutes. The retention time of the (1R, 4S)-isomer was about 22 minutes.

EXAMPLE 4 (-)-(1R, 4S)-tert-Butyl N- 4hydroxvmethyl)-2-cyclopenten-1-yl!carbamate

The first filtrate of Example 2 containing (-)-(1S,4R)-4amino-2-cyclopentene-1-mrethanol was cooled in an ice-acetone bathand treated with di-tert-butyl dicarbonate (199.42 g, 0.9265 mol,Aldrich). The mixture was concentrated under vacuum to a volume of 300mL, and added to the second filtrate of Example 2 that had meanwhilebeen cooled in an ice-acetone bath. The mixture was allowed to stir andwarm to room temperature over the course of 18 hours, during which timegas evolved and a clear solution formed. This solution was combined withthe last filtrate of Example 2 which had been evaporated under vacuum toa mixture of oil and solids. The resulting solution was evaporated undervacuum to an oil. The oil was partitioned between ethyl acetate (300 mL)and phosphate buffer (100 mL of 1.5 molar potassium dihydrogen phosphateadjusted to pH 7.0 with 50% sodium hydroxide-water). The phases wereseparated, the aqueous phase was reextracted twice with ethyl acetate(200 mL). The organic phases were dried over sodium sulfate and filteredthrough silica gel (50 g.). The solvent was removed under vacuum to givean oil (220.78 g), which was taken up in hexanes (300 mL) A minimumamount of ethyl acetate (about 50 mL) was added in order to dissolve theoil, and the solution was set to crystallize over the course of threedays. The crystals were filtered off, washed with 20% ethylacetate/hexanes, and dried by suction to a constantweight (156.1 g,0.732 mol, 82.6% of theory) of the title compound; m.p. 73°-73.7° C.; ¹H-NMR (DMSO-d₆)δ: 6.72 (d, J=7.9 Hz 1H, NH), 5.80 and 5.60 (two m, 2H,CH=CH), 4.59 (t,J=5.2 Hz, 1H, OH), 4.45 (m, 1H, CHN), 3.35(m,overlapping H₂ O, CH₂ O),2.60(m, 1H, CH),2.30(m, 1H, 1/2CH₂),1.40(s, 9H,C(CH₃)₃), 1.2 (m, 1H, 1/2CH₂); α!²⁰ ₅₈₉ -2.78°, α!²⁰ ₃₇₈ -2.84°, α!²⁰₅₄₆ -3.06°, α!²⁰ ₄₃₆ -3.39°, α!²⁰ ₃₆₅ -0.95°(c=5.07, methanol); Cl-MS(CH₄ )214 (M+1); TLC (silica, 10% methanol-chloroform, iodinevisualization), R_(f) =0.51.

Anal. Calcd. for C₁₁ H₁₉ O₃ N: C, 61.95; H, 8.98, N, 6.57.

Found: C, 61.87; H, 8.96; N, 6.59.

An additional 10.14 g of crystalline material was recovered from themother liquor by crystallization and chromatography, bringing the totalyield to 166.24 g (0.780 mol, 87.9% of theory from-the lactam startingmaterial of Example 1).

It was also found convenient to prepare the title compound directly from2-azabicyclo 2.2.1!hept-5-en-3-one, either racemic or the (-)enantiomer, as follows. (-)-2-Azabicyclo 2.2.1!hept-5-en-3-one (6.00 g,55.0 mmol) in anhydrous tetrahydrofuran (30 mL) was warmed to 34° C. andstirred while methanesulfonic acid (3.6 mL, 55 mmol) and water (0.99 mL,55 mmol) were added dropwise over 10 minutes. An exotherm of 10° C. wasobserved within 5 minutes and a crystalline solid began to precipitate.The mixture was refluxed (oil bath at 74° C.) for 2.5 hours. The mixturewas cooled to -10° C. and a solution of lithium aluminum hydride(1.0 Min tetrahydrofuran, 100 mL) added. The first 15 mL was added over 10minutes and an exotherm of 7° C. noted. The remaining 85 mL was addedrapidly with no further exotherm noted. The mixture was brought toreflux over 30 minutes and reflux continued for 18 hours. The mixturewas cooled to 25° C. and sodium fluoride (25.2 g, 0.600 mole) was addedand, after stirring for 30 minutes water (5.3 mL) was added dropwiseover 10 minutes to the cooled (0° C.) mixture. The mixture was stirredfor 30 minutes at 25° C. and di-tert-butyl dicarbonate (12.6 mL, 55.0mmol) was added. This mixture was stirred for 16 hours, filtered, andthe cake triturated with ethyl acetate (2×50 mL). The combinedfilterate-wash was washed with water (20 mL), dried (Na₂ SO₄),evaporated, and the residual syrup crystallized from ethylacetate:hexanes/ 1:2(30 mL) to give title compound as white crystals(10.32 g, 88%), identical in properties to the above described sample.

EXAMPLE 5 (-)-(1R, 2S, 3R, 4R)-tert-Bulyl N-2,3-dihydroxy-4-(hydroxymethyl)-1-cyclopentyl!carbamate

To a mixture of N-methyl morpholine-N-oxide (146.2 g, 60% in water,0.749 mol) and osmium tetroxide (75 g, 2.5% in tert-butanol, 0.959 mmol)in acetone (1L) stirring at -8° C. in an ice-acetone bath was added inone portion (-)-(1R, 4S)-tert-butyl N- 4-hydroxymethyl)-2-cyclopenten1-yl! carbamate (152.10 g, 0.7132 mol, from the preceding Example). Theresulting mixture was allowed to warm to roam temperature over 16 hours.during which time it became homogeneous. More osmium tetroxide was added(2.602 g, 0.256 mmol), and the solution was stirred at 20° C. for fourhours, then 40° for two hours, at which time the reaction was judgedcomplete by TLC (silica, 10% methanol-chloroform visualization withiodine followed by vanillin char, starting material. R_(f) =0.51products: R_(f) =0.22,(2S, 3R)-isomer, and R_(f) =0.36,(2R, 3S)-isomer).The ratio of (2S, 3R)/(2R, 3S) isomers was about 73:27 as judged by ¹H-NMR and TLC. Water (75 mL) was added, followed by chloroform (2 L).The resulting two phase mixture was cooled in an ice bath, and with verygentle agitation (to discourage phase mixing), anhydrous copper sulfate(457.8 g, Alfa) was added in several portions. The resulting slurry wasallowed to stir at room temperature about 16 hours, then was filteredwith filter aids (Celite 545 and 512). The cake was washed withtetrahydrofuran (6 L) until no more product eluted. The filtrate wasevaporated under vacuum to a dark oil substantially free of N-methylmorpholine. The oil was filtered through silica gel (300 g), and elutedwith tetrahydrofuran (3 L) until all of the product was eluted. Theeluate was concentrated to 200 mL, and hexanes (about 300 mL) was added.Crystallization began spontaneously, and was allowed to continue at -5°C. for about 16 hours. The crystals were recovered by filtration, washedsparingly with 50% ethyl acetate-hexanes, and dried by suction to aconstant weight(105.78 g, 0.428 mol, 60.0% of theoretical).Recrystallization from refluxing ethyl acetate (200 mL) provided thetitle compound as white crystals (93.85 g, 0.3795 mol, 53.2% oftheoretical); m.p. 115.8°-117°; ¹ H-NMR (DMSO-d₆)δ: 6.71 (br d,J=7.4 Hz,1H, NH), 4.52(t,J=5.2 Hz, 1H, CH₂ OH)4.43(d, J=5.1 Hz, 1, CHOH, 4.31(d,J=4.9 Hz, 1 H, CHOH), 3.54-3.41 (overlapping multiplet, 3H, CHN andCHOH),3.34 (m, overlapping with HOD, w1/2=20 Hz, CH₂ OH), 1.99 (dt,J=12.5, 6.8, 6.8 Hz, 1H, HOCH₂ CH),1.85(br.m, w1/2=30 Hz, 1 H,1/2CH₂),1.39 (s, 9H, C(CH₃)₃), 0.98(dt, J=12.4, 7.8, 7.8 Hz, 1H,1/2CH₂); α!²⁰ ₅₈₉ -8.08°, α!²⁰ ₅₇₈ -8.57 °, α!²⁰ ₅₄₆ -9.95°, α!²⁰ ₄₃₆-18.22, α!²⁰ ₃₆₅ -29.36° (c=1.02, methanol); Cl-MS (CH₄) 248(M+1).

Anal. Calcd. for C₁₁ H₂₁ O₅ N: C, 53.43; H, 8.56; N, 5.66.

Found: C, 53.45; H8.58; N, 5.69.

A sample of the (-)-(2R, 3S)-isomer(25.60 g) was obtained from themother liquors by fractional crystallization from ethyl acetate; m.p.106°-107.2° C.; ¹ H-NMR (DMSO-d₆)δ:5.93 (br d,J=7.6 Hz, 1 H,NH),4.77(d,J=4.9 Hz, 1H, CHOH),4.58(d,J=4.1 Hz, 1H, CHOH),4.35 (br t,w1/2=15 Hz, 1H, CH₂ OH),3.89 (br s, w 1/2 =10 Hz, 1H, OCH), 3.73 (br s,2H, OCH, NCH), 3.50 (br m, w1/2=20 Hz, 1 H, 1/2OCH₂),3.38 (br m,obscured by HOD, 1/2OCH₂), 1.90(m, w1/2=24 Hz, 2H, OCH₂ CH, 1/2CH₂),1.38(s, 9H, C(CH₃)₃),1.27 (m, 1H, 1/2CH₂); α!²⁰ ₅₈₉ -7.92 °, α!²⁰ ₅₇₈-8.14 °, α!²⁰ ₅₄₆ -9.05°, α!²⁰ ₄₃₆ -14.81°, α!²⁰ ₃₆₅ -21.19°(c=1.36,methanol); Cl-MS (CH₄), 248(M+1).

Anal. Calcd. for C₁₁ H₂₁ O₅ N, 0.05H₂ O: C, 53.23; H, 8.57; N, 5.64.

Found: C, 53.20; H, 8.55; N, 5.61.

EXAMPLE 6 (-)-(6aR, 8R, 9S, 9aR)-tert-ButylN-(hexahydro-9-hydroxy-,2,4,4-tetraisopropyl cylopentaf!-1,3,5,2,4-trioxadisilocin-8-yl) carbamate

The product of the preceding Example, (-)-(1R, 2S, 3R, 4R)-tert-butyl N-2,3-dihydroxy-4-(hydroxymethyl)-1-cydopentyl! carbamate (92.97 g, 0.3760mol) and imidazole (103.0 g, 1.513 mol, Aldrich) were dissolved in dryN,N-dimethylformamide (200 mL Aldrich) and cooled to -7° C. in anice-acetone bath. With rapid stirring,1,3-dichloro-1,1,3,3-tetraisopropyl disiloxane (121.2 g, 0.3842 mol,Cambridge, refractionated) was run in at once (about 1/2 minute), andimmediately washed in with cyclohexane (10 mL). An immediate exothermcarried the temperature to 35° C., then subsided. At 10° C., the coolingbath was removed and the mixture was allowed to stir at room temperaturefor two days. The reaction mixture was partitioned between cyclohexaneand ice water (200 mL each). The lower phase (pH=7) was extracted withtwo additional portions of cyclohexane (200 mL each), and each of theorganic extracts was then washed in sequence with four portions ofwater(150 mL) and one portion of saturated aqueous sodium sulfate. Theorganic phases were dried over anhydrous sodium sulfate, then filteredand concentrated under vacuum to a volume of about 250 mL(slightlyyellow solution), which was used directly in the following Example.

A sample of the title compound prepared similarly but purified bychromatography on silica gel (eluted with 20% ethyl acetate-hexanes)gave a colorless glass, which crystallized on standing with thefollowing characteristics; m.p. 63.5°-65.2° C.; ¹ H-NMR (DMSO-d₆)δ: 6.96(br d, J=4.8 Hz, 1H, NH), 4.24 (d, J=4.8 Hz, 1H, OH),3.93 (dd, J=7.3,5.5 Hz, 1H, NCH),3.83 (dd, J=13,2.7 Hz, 1H, OCH),3.65(q, J=4.7 Hz, 2H,CH₂ O), 3.53 (br d, J˜6 Hz, 1H, OCH), 2.09-1.80 (br m, 2H, CH and1/2CH₂),1.39 (s 9H, C(CH₃)₃), 1.04(m, w1/2=13 Hz, 29H,CH (CH₃)₂ and1/2CH₂, obscured); α!²⁰ ₅₈₉ -15.45 °, α!²⁰ ₅₇₈ -16.23°, α!²⁰ ₅₄₆-19.21°, α!²⁰ ₄₃₆ -33.62°, α!²⁰ ₃₆₅ -52.43° (c=0.779,methanol, correctedfor 0.3 H₂ O); Cl-MS (CH₄): 490(M+1); TLC (silica, 20% ethylacetate-hexanes, iodine visualization) R₄ =0.46.

Anal. Calcd. for C₂₃ H₄₇ NO₆ Si₂ ·0.3H₂ O: C, 55.79; H, 9.69; N, 2.83.

Found: C, 55.81; H, 9.57; N, 2.82.

EXAMPLE 7 (-)-(6aR, 8R, 9S, 9aR)-tert-ButylN-(hexanydro-2,2,4,4-tetraisopropyl-9-((phenoxythiocarbonyl)oxy)-cyclopentaf!-1,3,5,2,4-trioxadisilocin-8-yl)carbamate

The solution of (-)-(6aR, 8R, 9S, 9aR)-tert-butylN-(hexahydro-9-hydroxy-2,2,4,4-tetraisopropylcyclopentaf!-1,3,5,2,4-trioxadisilocin-8-yl) carbamate (0.3760 mol) incyclohexane, obtained in the preceding Example was diluted to a totalvolume of 500 mL with cyclohexane. N-Hydroxysuccinimide (8.568 g, 74.45mmol), and pyridine (33.2 mL, 0.410 mol) were added, then with rapidstirring, a solution of phenyl thionochloroformate (70.8 g, 0.410 mol)in cyclohexane (50 mL) was added dropwise over the course of 20 minutes.The resulting dark mixture was stirred for 16 hours at room temperature,then refluxed for four hours. Pyridine (7.1 mL, 88 mmol), thenphenylthionochloroformate (15.09 g, 87.41 mmol)were added, and themixture was refluxed for three hours. Pyridine (5.0 mL, 62 mmol) andphenylthionochloroformate (9.903 g, 57.37 mmol)were added, and themixture was refluxed an additional 3.5 hours, at which time it wasjudged complete by TLC (silica, 20% ethyl acetate-hexanes, visualizationwith iodine followed by vanillin char; starting material: R_(f) =0.46,product: R_(f) =0.49). The mixture was distilled to a volume of about400 mL, cooled to room temperature, then filtered through a bed offilter aid (1 cm, Celite 545) under a dry nitrogen atmosphere. Theresulting cake of pyridine hydrochloride was washed with cyclohexane(200 mL), to give a solution of the title compound in cyclohexane.

A sample prepared similarly, but purified by chromatography on silicagel (eluted with 10% ethyl acetate-hexanes) gave a colorless oil withthe following characteristics; ¹ H-NMR (DMSO-d₆)δ: 7.56-7.28(m, 4H, o-and m-ArH),7.11 (br d, J=7.3 Hz, 2H, NH and p-ArH),5.49 (dd, J=5.3, 3.3Hz, 1H, SCOCH), 4.33 (br m, w1/2=20 Hz, 1H, NCH),3.88 (m, 2H, 1/2CH₂ Oand OCH), 3.71(br dd, J˜12, 3 Hz, 1H, 1/2OCH₂),2.11-1.88 (br m, 2H,1/2CH₂ and CH),1.40(s, 9H, C(CH₃)₃),1.05(d, J=4.9 Hz, overlapping withmultiplet, 29H, 1/2CH₂ +4CH(CH₃)₂); α!²⁰ ₅₈₉ -3.17°, α!²⁰ ₅₇₈ -33.1°,α!²⁰ ₅₄₆ -37.4°, α!²⁰ ₄₃₆ -61.3°, α!²⁰ ₃₆₅ -71.4° (c=1.19, methanol,corrected for 0.15 methylene chloride, 0.10 ethyl acetate and 0.10water);

Anal. Calcd. for C₃₀ H₅₁ O₇ NSi₂ S·0.15CH₂ Cl₂ ·0.10C₄ H₈ O₂ ·0.10H₂ O:C, 56.51; H, 8.12; N, 2.16; S, 4.94

Found: C. 56.77; H, 8.41; N, 2.19; S, 4.98.

EXAMPLE 8 (-)-(6aR, 8R, 9aS)-tert-ButylN-(hexahydro-2,2,4,4-tetraisopropyicyclopentaf!-1,3,5,2,4-trioxadisilocin-8-yl) carbamate

The cyclohexane solution of (6aR, 8R, 9S, 9aR)-tert-butylN-hexahydro-2,2,4,-tetraisopropyl-9-(phenoxythiocarbonyl)oxy!-cyclopenta f!-1,3,5,2,4-trioxadisilocin-8-yl)carbamate (0.3760 mol) prepared in the previous Example was degassedunder a nitrogen atmosphere. Tributyltin hydride (207.4g, 0.713 mol) and2,2'-azo bis(2-methylpropionitrile) (12.79 g, 77.86 mmol) were added,the degassing was repeated, and the black solution was refluxed for fourhours, during which time it turned to an amber color, and the reactionwas judged complete by TLC (silica, 20% ethyl acetate-hexanes,visualized with iodine followed by vanillin char, starting material:R_(f) =0.49, product: R_(f) =0.36, white spot). The reaction solutionwas cooled to room temperature and added to 5% ammonium hydroxide-water(500 mL). The lower (aqueous) phase was extracted with two portions ofhexane (200 mL each), and each of the organic extracts was then washedin sequence with 5% aqueous ammonia (two 500 mL portions, to removephenol) water (500 mL), and saturated aqueous sodium sulfate (200 mL).The combined organic extracts were dried over sodium sulfate, thenapplied to a column of silica gel (about 1 Kg), which was eluted withhexanes (1 L), 5% ethyl acetate-hexanes (1 L), 20% ethyl acetate-hexanes(1 L) and ethyl acetate. All fractions containing product wereevaporated to an amber oil (322.5 g). This was further purified bychromatography on two columns of silica gel (1 Kg each, eluted with anethyl acetate- hexanes gradient) giving the title compound in twoportions as an oil (74.32 g and 73.82 g, respectively, total 148.14 g,0.313 mol, 83.2% of theoretical from the trial product of Example 5). Asample prepared similarly, but taken as the central fraction of thechromatography gave a colorless, crystallizing glass with the followingcharacteristics:

m.p. 66°-67.0° C.; ¹ H-NMR(DMSO-d₆),δ: 6.93 (br d, J=6 Hz, 1H, NH),4.22(q, J=6.8 Hz, 1H, NCH),3.84 (dd, J=3.1, 11.5 Hz, 2H, CH₂ O), 3.61(dd, J=6.5, 9 Hz, 1H, OCH), 1.91-1.73 (br m, 4H, CH, 1/2CH₂, CH₂),1.38(s, 9H, C(CH₃)₃)1.02(m, w1/2=21 Hz, 29H, 4CH₃)₂ and 1/2CH₂,obscured); α!²⁰ ₅₈₉ -2.78°, α!²⁰ ₅₇₈ -2.84°, α!²⁰ ₅₄₆ -3.06°, α!²⁰ ₄₃₆-3.39°, α!²⁰ ₃₆₅ -0.95°(c=5.07,methanol);Cl-MS(CH₄): 474(M+1).

Anal. Calcd. for C₂₃ H₄₇ NO₅ Si₂ C, 58.31; H, 10:00; N, 2.96.

Found: C, 58.33; H, 10.00; N, 2.97.

EXAMPLE 9 (+)-(1R, 3S, 4R)-tert-Butyl N-3-hydroxy-4-(hydroxymethyl)-1-cyclopentyl!carbamate

To a solution of (-)-(6aR, 8R, 9aS)-tert-butylN-(hexahydro-2,2,4,4-tetraisopropylcyclopentaf!-1,3,5,2,4-trioxadisilocin-8-yl) carbamate (74.32 g, 0.1569 mol,corresponding to the first portion of product in the above Example) intetrahydrofuran (300 mL) was added tetraethyl ammonium fluoride hydrate(24.62 g, about 0.15 mol, Aldrich). The lumps of solid were broken up,the mixture was degassed (nitrogen), then refluxed for 45 minutes. Aftercooling to room temperature. the reaction mixture was applied to acolumn of silica gel (200 g) and eluted with tetrahydrofuran (3 L). Theeluate was concentrated under vacuum to an amber oil, which was taken upin hexanes (150 mL). Crystallization began spontaneously, and wasallowed to continue at -5° for two days. The crystals of crude titlecompound were collected by filtration, washed sparingly with 10% ethylacetate-hexanes, and dried by suction to constant weight (25.08 g,0.1084 mol). The procedure was repeated on the second portion of productfrom the above Example(73.82 g, 0.1558 mol), giving additional crudetitle compound (27.28 g, 0.1180 mol). The two portions of crude titlecompound were combined and recrystallized from boiling ethyl acetate(250 mL), giving white crystals of the title compound (46.67 g., 0.2018mol, 53.7% of theoretical from the triol product of Example 5) havingthe following characteristics: m.p. 126°-127.9° C.; ¹ H-NMR (DMSO-d₆),δ:6.75 (br d, J=7.8 Hz, 1H, NH),4.49(t, J=4.5 HZ,CH2OH) overlapping4.47(d, J=4.3 Hz, CHOH) with total integration of 2H, 3.80-3.93 (m, 2H,CHN and CHOH), 3.34(m, w1/2=20 Hz, CH₂ OH), 2.25(dt, 1H,CHCH₂),1.79-1.63(m, 2H, CH₂ CHOH), 1.63-1.50m, 1H, 1/2CH₂), 1.38(s, 9H,C(CH₃)₃), 1.11-0.96(m, 1H, 1/2CH₂); Cl-MS(CH₄): 232(M+1).

Anal Calcd. for C₁₁ H₂₁ O₄ N: C, 57.12; H, 9.15;N, 6.06.

Found; C, 57.07; H, 9.12; N, 6.08.

A chromatographically homogeneous sample of the title compound preparedsimilarly showed: α!²⁰ ₅₈₉ +15.4°, α!²⁰ ₅₇₈ +14.0°, α!²⁰ ₅₄₆ +18.2°,α!²⁰ ₄₃₆ +30.4°, α!²⁰ ₃₆₅ 43.7° (c=0.51, methanol, corrected for 0.13 H₂O solvation).

EXAMPLE 10 (+)-(1S, 2R, 4R)-4-Amino-2-(hydroxymethyl)-1-cyclopentanol

The product of the preceding Example, (+)-(1R, 3S, 4R)-tert-butyl N-3-hydroxy-4-(hydroxymeythyl)-1-cyclopentyl! carbamate (2.351 g, 10.17mmol) was slurried in aqueous hydrochloric acid (1.0 molar, 25.4 mL,25.4 mmol) and heated gently (60°-80°C.) until a colorless solutionformed, and the gas evolution subsided (about 15 minutes). The solutionwas allowed to cool to room temperature, then was concentrated undervacuum to a syrup, which was taken up in water (about 20 mL) andreconcentrated. The resulting syrup of hydrochloride salt was applied toa column of quaternary amine ion exchange resin (about 50 mL ofAmberlite IRA400, hydroxide form, washed to neutrality with water), andeluted with water (500 mL)-The water was evaporated under vacuum,leaving the title compound as a colorless syrup (1.62 g). ¹H-NMR(DMSO-d₆),δ:3.90(dt, J=4.7, 4.7, 6.4 Hz, 1H, NCH), 3.47-3.23(m,obscured by broad OH peak, ˜3H, CH₂ O and CHO), 1.97(dt, J=7.3, 7.3,12.7 Hz, 1H, CHCH₂ OH), 1.78(br sextet, J=5Hz, 1H, 1/2CH₂), 1.61(m,w1/2=22 Hz, 1H, 1/2CH₂), 1.47 (m, w1/2=30 Hz, 1H, 1/2CH₂), 0.94(dt,J=7.2, 7.2, 12.3 Hz, 1H, 1/2CH₂); α!²⁰ ₅₈₉ +35.9°, α!²⁰ ₅₇₈ +37.3°, α!²⁰₅₄₆ +42.3°, α!²⁰ ₄₃₆ +69.9°, α!²⁰ ₃₆₅ +103.0°,(c=2.49 methanol,corrected for 1.3 H₂ O); Cl-MS(CH₄): 132(M+1).

Anal. Calcd. for C₆ H₁₃ O₂ N·1.3H₂ O: C, 46.62; H, 10.1.7; N, 9.06.

Found: C, 46.61; H, 9.99; N, 8.93.

EXAMPLE 11 (±)-cis-4-Amino-2-cyclopentene-1-carboxylic acid,4-toluenesulfonate

A 500 mL, three-neck flask with vertical joints was charged with(±)-2-azabicyclo 2.2.1! hept-5-en-3-one (48.66 g, 0.4459 mol,Cambridge), and equipped with a mechanical stirrer, thermometer with gasinlet adapter connected to the nitrogen supply, and a powder funnel.Tetrahydrofuran (200 mL, reagent grade) was added, and the stirrerstarted in order to dissolve the solid. An endotherm of 13° C. wasnoted. A gentle nitrogen sweep was applied from the inlet adapter outthe powder funnel and 4-toluene sulfonic acid hydrate (93.52 g, 0.416mol, 1.1 equv) was added, along with a small amount of the titlecompound as seed. The powder funnel was replaced by a reflux condenser,and the flask was immersed in an oil bath preequilibrated to 35° C.Within 10 minutes, crystallization began, followed by an exothermpeaking at 60° C. in another 15 minutes. After the exotherm peaked, thebath was reset to 60°-65° C., and the reaction mixture was heated twohours at 60°-65° C. (internal), until a TLC of the supernatant liquid(silica, ethyl acetate eluent, iodine visualization) shows the absenceof starting lactam against an authentic spot. The mixture was thencooled in an ice bath to ˜5° C. A glass tube with a fritted end wasconnected via flexible tubing to a filter flask, in turn connected to avacuum source. The condenser was removed from the flask containing theslurry, the stirrer was stopped, and with a nitrogen sweep from the gasinlet, the fritted end of the stick was pushed to the bottom of theflask under the agitator. Vacuum was applied until the liquid wascompletely removed, the solids were reslurried in dry tetrahydrofuran(100 mL), and the filtration operation was repeated. The resulting whitesolids were reslurried in drytetrahydrofuran (200 mL), and the open neckwas capped with a septum. The resulting slurry of the title compound wasused directly in the following Example; an analytical sample wasprepared similarly, except that it was dried first by suction then bythe application of vacuum; 191°-193° C.; ¹ H-NMR(DMSO-d₆),δ: 12.62(br s,1H, CO₂ H), 7.93 (br s, 3H, NH₃ ⁺),7.47 and 7.11(dd, 8.0 Hz, 2H each,Ar--H), 6.11 (dt, J=5.7, 1.9, 1.9, Hz, 1H, vinyl), 5.82 (dt, J=5.7, 2.8,2.8 Hz, 1H vinyl), 4.20 (br m,w1/2=21 Hz, 1H, allylic H), 3.61 (br tt?,w1/2=21 Hz, 1H, allylic),2.29(s, 3H, CH₃), 2.50 (dt?, J=5.8, 5.8, 11.5Hz, (overlapping DMSO peak), 1/2CH₂), 1.92 (dt, J=6.7, 6.7, 13.4 Hz, 1H,1/2CH₂).

Anal. Calcd. for C₁₃ H₁₇ O₅ N₅ : C, 52.16; H, 5.72; N, 4.68; S, 10.71.

Found: C, 52.16; H, 5.76; N, 4.66; S, 10.62.

EXAMPLE 12 (±)-cis-4-Amino-2-cvclopentene-1-methanol

A dry, 2L. three-neck flask was equipped with a mechanical stirrer,thermometer with gas inlet adapter connected to the nitrogen supply, andseptum. The flask was purged with nitrogen, immersed in an ice-acetonebath, and lithium aluminum hydride solution in tetrahydrofuran (1.0molar, 800 mL, 0.80 mol, Aldrich) was added via cannula. Drytetrahydrofuran (2×15 mL) was used to rinse in the lithium aluminumhydride solution.

When the solution had cooled to 0° C., the slurry of(±)-cis4-amino-2-cyclopentene1-carboxylic acid 4-toluenesulfonatesalt intetrahydrofuran prepared in the previous Example was cannulated in withgood stirring, at such a rate as to keep the temperature less than 10°C. and moderate the hydrogen evolution (about one hour). The flask wasrinsed with dry tetrahydrofuran (2×15 mL), and the septum was replacedwith a reflux condenser. The resulting clear, light amber solution wasslowly warmed to a gentle reflux over the course of two hours, at whichpoint it became cloudy. After refluxing overnight (16 hours), theheating bath was dropped, sodium fluoride (136.3 g, 3.25 mol, reagentgrade powder) was added, and the condenser reset for downwarddistillation. The mixture was distilled to a thin slurry(700 mL ofdistillate collected),then cooled in an ice bath. Diethyl ether(dry, 500mL) was added, and the condenser was replaced by an addition funnelcontaining water (43 mL, 2.4 mol). The water was added very slowly (twohours), with care taken to control the rate of hydrogen evolution andmaintain the temperature at 10°±5° C. Meanwhile, water (54 mL) was addedto the above recovered distillate, and sufficient additionaltetrahydrofuran was added to bring the total volume to 900 mL (6% H₂ O).The reaction mixture was filtered by suction, and the cakedisplace-washed with tetrahydrofuran (100 mL). Part of the 6%water-tetrahydrofuran solution (300 mL)was used to slurry-wash the cake,which was-then returned to the reaction flask. The cake was triturated(25 minutes) in 6% water-tetrahydrofuran (400 mL), filtered, anddisplace-washed with 6% water-tetrahydrofuran (200 mL). The combinedfiltrates were concentrated to a pale yellow oil under vacuum.(44.07 g,67.8% by HPLC, see Example 3). This oil, containing pure title compound,water, and a trace of tosylate salt, darkens rapidity under ambientconditions. It was immediately reacted to form the N-BOC derivative, astable, crystalline solid, (see the following Example). The filter cakewas returned to the flask and triturated in methanol (800 mL) for 48hours. The resulting slurry was filtered under a rubber dam, and thecake was washed with, methanol (200 mL). The filtrate was concentratedunder vacuum to a yellow solid (56.80 g, 20.9% yield by HPLC; totaloverall yield 88.7%). This extract was also taken to the N-BOCderivative (see the following Example).

EXAMPLE 13 (±)-cis-tert-Butyl N- 14-(hydroxymethyl)-2-cyclopenten-1yl!carbamate

The first extract of the previous example containing(±)4-Amino-2-cyclopentene-1-methanol (0.4459 mol) was dissolved in 2:11,4-dioxane-water (1.2 L). Sodium bicarbonate (48.69 g, 0.580 mol) wasadded, the mixture was cooled in an ice-water bath anddi-tert-butyidicarbonate (110.25 g, 0.490 mol, Aldrich 97%) was added inone portion with rapid stirring. The resulting mixture was warmed toroom temperature over the course of one hour, then was concentratedunder vacuum to a volume of about 400 mL The slurry was taken up inchloroform (300 mL), the phases were separated, and the aqueous (upper)phase was reextracted with chloroform (five portions of 300 mL each)until no product was observed in the extract by TLC (silica, 10%methanol-chloroform, iodine visualization, Rf=0.51). The combinedorganic phases were dried over sodium sulfate, filtered and concentratedunder vacuum to give the title compound as an oil. The final extract ofthe previous example was reacted similarly, and the crude title compoundthus obtained was combined with the above portion, the combined materialwas taken up in hexanes and evaporated under vacuum to remove residualchloroform. The oil then crystallized spontaneously. It was trituratedin cold hexanes and filtered to give the crude title compound as acrystalline solid, which was dried by suction to a constant weight(79.98 g, 0.3750 mol). Recrystallization from boiling ethyl acetate (70mL) and hexanes (300 mL) gave the title compound as a off-white,crystalline solid (73.43 g, 0.3443 mol); m.p. 55°-55.5° C.; ¹ H -NMR(DMSO--d₆)δ: 6.72 (d, J =7.9 Hz, 1H, NH),5.80 and 5.60 (two m, 2H,CH=CH), 4.59 (t, J=5.2 Hz, 1H, OH), 4.45 (m, 1H, CHN), 3.35 (m,overlapping H₂ O, CH₂ O), 2.60 (m, 1 H, CH), 2.30(m, 1H, 1/2CH₂), 1.40(s, 9H, C(CH₃)₃), 1.2 (m, 1H, 1/2CH₂).

Anal. Calcd. for C₁₁ H₁₉ NO₃ : C, 61.94; H, 8.98; N, 6.57.

Found: C, 62.00; H, 8.99; N, 6.55.

The mother liquors were combined, chromatographed on silica gel (700 g,30% ethyl acetate-hexanes and 5% methanol-chloroform), and crystallizedas above to give a second portion of the title compound (10.499, 0.0492mmol). The total yield was thus 0.3935 mol, or 88.9% of theoretical fromthe starting (±)-2-azabicyclo 2.2.1!hept-5-en-3-one (corrected foraliquots taken).

EXAMPLE 14 (±)-cis4-Amino-2-cyclopentene-1-methanol

By the method of Examples 11 and 12, but on about twice the scale(97.40g, 0.8924 mol of (±)-2-azabicydo 2.2.1!hept-5-en-3-one) the titlecompound was obtained as extracts containing the title compound (0.7926mol, 88.8% of theoretical, allowing for aliquots removed, as determinedby the method of Example 3).

EXAMPLE 15 (±)-cis-tert-Butyl N-(4- hydroxymethyl)-2cyclopenten-1-yl!carbamate

The combined tetrahydrofuran extracts from the preceding Example wereconcentrated under vacuum to 1031 g, cooled in an ice-water bath, and amixture of sodium bicarbonate (97.46 g, 1.16 mol) in water (500 mL) wasadded. This was followed by di-tert-butyl dicarbonate (204.5 g), 0.9501mol). The mixture was stirred at 5° C. for two days. The methanolextracts from the preceding Example were evaporated to an oily solid(136.64 g), which was added to the mixture. After warming to roomtemperature, the organic solvents were evaporated under vacuum, and theresulting slurry was extracted with hexanes, three portions of methylenechloride, then hexanes again (200 mL each). The organic extracts wereevaporated to an oil, which was crystallized from hexanes (about 300mL), giving the title compound (154.15 g, 0.7229 mol), identical to theproduct of Example 13. Additional product was obtained by chromatographyof the mother liquors (10.5 g, 0.0491 mol, 86.6% of theoretical from thestarting lactam, allowing for aliquots removed).

EXAMPLE 16 (±)-cis-4-Amino-2-cyclopentene-1-carboxlic acid,methanesulfonate

Beginning with (±)-2-azabicyclo 2.2.1!hept-5-en-3-one (5.111 g, 46.83mmol, Cambridge), by the method of Example 1, was prepared the titlecompound (10.268 g, 45.99 mmol, 98.2%);m.p. 137°-139° C., ¹H-NMR(DMSO--d₆)δ: 12.6(br s, 1H, CO₂ H), 8.04 (br s, 3H, NH₃ ⁺), 6.10(dt, J=5.6, 2.0, 2.0 Hz, 1H, vinyl), 5.85(dt, J=5.3, 2.3, 2.3 Hz, 1H,vinyl), 4.19(br s., w1/2=20 Hz, 1H, allylic H), 3.61(m, w1/2=22 Hz, 1H,allylic H). 2.53 (quintet, J=5.3 Hz (overlapping with DMSO peak), 1/2CH₂), 2.39(s, 3H, CH₃ SO₃ H), 1.93 (dt, J=6.7, 6.7, 13.7 Hz, 1H,1/2CH₂);Cl-MS(CH₄): 128(M+1); El-MS: 127(M).

Anal. Calcd. for C₇ H₁₃ NO₅ S: C, 37.66; H, 5.87; N, 627: S, 14.36

Found: C, 37.60; H, 5.85; N, 6.25;S, 14.30

EXAMPLE 17 (±)-cis-4-Amino-2-cyclopentene-1-carboxylic acid,4-toluenesulfonate

To a solution containing a catalytic amount of 4-toluene sulfonic acid(10 mg) in 30% aqueous hydrogen peroxide (0.30 mL, 2.7 mmol) was added3-tosyl-2-azabicyclo 2.2.1! hepta-2,5-diene (369 mg, 1.49 mmol),prepared by the method of J. C.Jagt and A. M. van Leusen, J. Org. Chem.1974, 39, 565-566, in portions, with rapid stirring. A large exotherm isnoted, stabilizing at 75° C. during the last half of the addition. Afterstirring 70° C. for 40 minutes, the mixture was repeatedly diluted withwater (6 mL total) and filtered until a clear solution resulted. Thesolution was evaporated to an oil which crystallized (349 mg). This wastriturated in tetrahydrofuran, filtered, and dried under vacuum to givethe title compound (202 mg, 45.2% of theoretical), ¹ H-NMR spectrumidentical to the product of Example 11.

EXAMPLE 18 (±)-(1R*, 2S*, 4S*)-4-2-Amino-6-(Cylopropylmethvlamino)-9H-purin-9-vl!-2-(hydroxymethyl)-1-cyclopentanolDihydrochloride)

(±)-(1R*, 2S*,4S*)-4-(2-Amino-6-chloro-9H-purin-9-yl)-2-(hydroxymethyl)-1-cyclopentanol(250 mg, 0.88 mmol) (Shealy et al.; U.S. Patent No. 4,543,255; Sep. 24,1985) ethanol (1 mL), and cyclopropylmethylamine (4.0 mL) were refluxedunder nitrogen for 1.5 hours. The cooled solution was evaporated todryness after the addition of 1N sodium hydroxide (0.88 mL). The residuewas absorbed on silica gel. Title compound was eluted from a silica gelcolumn with 5% methanol-chloroform as a colorless glass(220 mg). Theglass was dissolved in absolute ethanol (8.5 mL) and diluted with 1Mhydrochloric acid in diethyl ether (5 mL). The resulting whiteprecipitate was washed with diethyl ether and dried to give thedihydrochloride of title compound as white powder (210 mg, 48%),m.p.>250° C.; mass spectrum (Cl), 301 (M+1).

Anal. Calcd. for C₁₅ H₂₂ N₆ O₂ ·2HCl: C, 46:04; H, 6.18, N, 21.48; Cl,18.12.

Found: C, 46.00; H, 6.21; N, 21.36; Cl, 18.05.

EXAMPLE 19 (±)-(1R*, 2S*, 4S*)-4-2-Amino-6-(cycloproplamino)-9H-purin-9-yl!-2-(hydroxymethyl)-1-cyclopentanolDihydrochloride

In the same manner as example 18, with cyclopropylamine, title compoundwas obtained as its dihydrochloride from ethanol-ether as a white powder(272 mg, 85% yield from 0.9 mmol of the 6-chloropurine), m.p. >250°;mass spectrum (Cl), 305 (M+1).

Anal. Calcd. for C₁₄ H₂ O N₆ O₂ ·2HCl·0.85 H₂ O: C, 42.83;H, 6.08; N,21.41; Cl, 18.06.

Found C, 42.84; H, 6.08; N, 21.40; Cl, 18.04.

EXAMPLE 20 (+)-(1S, 2R,4R)-4-(6Chloro-5-formamido-2-isobutyramido-4-pyrimidinyl)2-(hydroxymethyl)-1-cyclopentanol

(1R, 3S, 4R)-tert-ButylN-(3-hydroxy-4hydroxymethyl)-1-cyclopentyl)carbamate (5.00 g, 21.6mmol), 1N hydrochloric acid (44 mL, and dioxane (10 m) were stirred atambient temperature for two hours. This solution was evaporated tocolorless oil (3.92g). This oil was refluxed with triethylamine (9.0 mL)and N-(4,6-dichloro-5-formamido-2-pyrimidyl) isobutyramide (EP 434450,Jun. 26, 1991) (5.99 g, 21.6 mmol) in t-butyl alcohol (75 mL) for 1.0hour. The cooled solution was treated with 1N sodium hydroxide (44 mL)and evaporated to a syrup which was chromatographed on silica gel. Thetitle compound was eluted with MeOH:CHCl₃ /1:4 as a tan solid foam (6.79g, 83%). Such a sample was slurried in diethyl ether to give off-whitepowder, m.p.: collapses at 105°-108° C.; mass spectrum (Cl, CH₄) 372(m+1); ¹ H-NMR(DMSO):δ1.06(d, J=6.8 Hz, 6H),1.22(m, 1H), 1.80(m, 3H),2.19(m, 1H), 2.90(m, 1H), 3.35(m, 2H), 3.92(m, 1H), 4.57 (m, 3H), 7.11(d, J=7.8 Hz), 7.39 (d, J=7.8 Hz), 1H!; 7.89 (d, J=11.4 Hz), 8.16(s),1H!, 8.82(d, J=11.4 Hz), 9.29(s), 1H!, 10.17(s), 10.23(s), 1H!, α!²⁰ ₅₈₉+23.6°, α!²⁰ ₅₇₈₊ 24.9°, α!²⁰ ₅₄₆ +28.9°, α!²⁰ ₄₃₆ +53.4°, α!²⁰ ₃₆₅+96.2° (c=0.71, methanol).

Anal. Calcd for C₁₅ H₂₂ N₅ O₄ Cl·0.45 H₂ O·0.35 EtOH; C, 45.61; H, 6.36;N, 17.68; Cl, 8.95.

Found: C, 47.84; H, 6.19; N, 17.42; Cl, 9.02.

EXAMPLE 21 (+)-(1S, 2R,4R)-4-(2-Amino-6-chloro-9H-purin-9-yl)-2-(hydroxymethyl)cyclopentanol

(1S, 2R,-4R)-4-(6Chloro5-formanido-2-isobutramide-4pyrimidinyl)-2(hydroxymethyl)-1-cyclopentanol(6.25 g, 16.8 mmol) was maintained at 55° C. in 1N hydrochloric acid (85mL) for 4 hours. Evaporation gave a dark oil which was dissolved inN,N-dimethylformamide(20 mL) and triethylorthoformate (85 mL)-Theresulting solution was stirred at ambient temperature for 16 hours.Volatiles were removed under vacuum and the residual oil stirred in 1Nhydrochloric acid (100 mL) for 5 hours. The solution was neutralizedwith sodium hydroxide and evaporated to a brown syrup. Chromatography ansilica gel with methanol:chloroform/15:85 gave title compound as a solidfoam (3.9 g). Crystallization from acetonitrile-methanol (1:1) gavetitle compound as white crystals (2.59 g, 53%); m.p. 143°-144°; massspectrum (Cl, CH₄) 284 (M+1); ¹ H-NMR (DMSO):δ1.67 (m, 1H), 2.01 (m,2H), 2.17 (m, 1H),2.33 (m, 1H), 3.45 (m, 1H), 3.52(m, 1H), 4.09(m, 1H),4.65 (t, J=5.1 Hz, 1 H), 4.80 (d, J=4.0 Hz, 1H), 4.91 (m, 1H), 6.88(brs,2H), 8.25 (s, 1H), α!²⁰ ₅₈₉ +17.5°, α!²⁰ ₅₇₈ +18.3°, α!²⁰ ₅₄₆ +20.5°,α!²⁰ ₄₃₆ +34.2°, α!²⁰ ₃₆₅ +49.4° (c=0.67, methanol).

Anal. Calcd. for C₁₁ H₁₄ N₅ O₂ Cl·0.5 H₂ O: C, 45.13; H, 5.16; N, 23.92;Cl, 12.11.

Found: C, 45.05; H, 5.02; N, 23.73; Cl, 12.13.

EXAMPLE 22 (+)-(1S, 2R, 4R)-4-2-Amino-6-(cyclopropylmethylamino)-9H-purin-9-yl!-2-(hydroxymethyl)-1-cyclopentanol

In the same manner as for the racemate, Example 18, title compound wasisolated, after chromatography, as white solid foam (48% from 2.0 mmolesof (+)-(1S, 2R, 4R)-4-(2-amino-6-chloro-9H-purin-9yl)-2-(hydroxymethyl)cyclopentanol): m.p.: collapses at 79°-83°; massspectrum (Cl, CH₄): 319(M+1); ¹ H-NMR(DMSO-d₆)δ: 7.83 (s, 1, H-8),5.79(br s, 2, NH₂), 4.95-4.80(m, 1, CHN), 4.75 (d, J=4.0 Hz, 1, OH),4.64 (t, J=5.2 Hz, 1, CH₂ OH), 4.05(br m, 1, CHO), 3.60-3.35 (m, 2,CH₂O), 3.25-3.15(m, overlapping s at 3.25,4, CHNMe, CH₃), 2.35-2.20 (m,1,CH).2.20-2.0,(m, 1,1/2CH₂), 2.0-1.85(m, 2, methylene), 0.85-0.60(m, 4,2CH₂ of cyclopropyl); α!²⁰ ₅₈₉ ×10.6°, α!²⁰ ₅₇₈ +10.8°, α!²⁰ ₅₄₆ +12.3°,α!²⁰ ₄₃₆ +20.6°, α!²⁰ ₃₆₅ +31.3° (c=0.84, methanol).

AnaL. Calcd. for C₁₅ H₂₂ N₆ O₂ ·0.05 H₂ O·0.04 ETOH; C, 55.02; H, 7.11;N, 25.53.

Found: C, 55.02; H, 7.06; N, 25.59.

EXAMPLE 23 (+)-(1S, 2R, 4R)-4-2-Amino-6-(cyclopropylamino)-9H-purin-9-yl!-2-(hydroxymethyl)-1-cvclopentanol

(+)-(1S, 2R,4R)-4-(2-Amino-6chloro-9H-purin-9-yl)-2-(hydroxymethyl)cyclopentanol(425 mg, 1.5 mmol), cyclopropylamine (Aldrich, 1.4 mL), and ethanol (4mL) were refluxed for 3 hours. To the cooled solution was added 1Nsodium hydroxide (1.5 mL. The residual oil left on evaporation ofvolatiles under vacuum was chromatographed on silica gel. Title compoundwas eluted with methanol: ethyl acetate/15:85 as a white solid foamwhich solidified to white powder in methanol-acetonitrile (309 mg, 68%);m.p. 174°-176° C.; mass spectrum (Cl, CH₄)305 (M+1); ¹ H-NMR(DMSO-d₆)δ:7.79(s, 1, H-8); 7.25(d, J=2.9 Hz, 1, NH), 5.79(s, 2, NH₂),4.90-4.75(m,1, CH-N), 4.73 (d, J=4.0 Hz, 1, OH), 4.63(t, J=5.3 Hz, 1,CHOH),4.08-4.00(m, 1, CHO), 3.58-3.38(m, 2, CH₂ O), 3.05-2.95(m,1CH-NH), 2.35-2.20(m, 1, CH),2.18-2.0(m, 1,1/2CH₂)2.0-1.9(m, 2,methylene), 1.7-1.5(m, 1,1/2CH₂), 0.70-0.50(m, 4, 2CH₂ of cyclopropyl);α!²⁰ ₅₈₉ +7.72°, α!²⁰ ₅₇₈ +7.87°, α!²⁰ ₅₄₆ +8.77°, α!²⁰ ₄₃₆ +14.4°, α!²⁰₃₆₅ +20.1°(c=0.66, methanol).

Anal. Calcd. for C₁₄ H₂₀ N₆ O₂ : C, 55.25; H, 6.62; N, 27.62.

Found: C, 55.21; H, 6.59; N, 27.54.

EXAMPLE 24 (+)-(1S, 2R,4R)-4(2-Amino-1,6-dihydro-6-thioxo-9H-purin-9yl)-2hydroxymethyl)-1-cyclopentanol

(+)-(1S, 2R,4R)-4-(2-Amino-6chloro-9H-purin-9-yl)-2-(hydroxymethyl)cyclopentanol.(1.70 g, 6.00 mmol) and thiourea (456 mg, 6.00 mmol) were refluxed inwater (15 mL) for 1.0 hour. The cooled solution was adjusted to pH5 withsaturated aqueous sodium bicarbonate. The resulting precipitate wasfiltered, washed with water and dried to give title compound as whitepowder (1.20 g, 71%); m.p. 290°-291° dec; mass spectrum (Cl, CH₄) 282(M+1); ¹ H-NMR (DMSO-d₆)δ:11.90 (br s, 1, NH), 8.03(s, 1, H-81)6.78 (brs, 2, NH₂), 4.95-4.70 (m, overlapping d at 4.78, J =27 Hz, total 2,CHNand OH)4.7-4.6 (m, 1, CH₂ OH), 4.1-4.0 (m, 1, CHOH),3.6-3.4(m, 2, CH₂O),2.4-2.2 (m, 1,CH), 2.2-1.9 (m, 3, methylene), 1.7-1.5 (m, 1, 1/2CH₂);α!²⁰ ₅₈₉ +6.43°, α!²⁰ ₅₇₈ +6.71°, α!²⁰ ₅₄₆ +7.43°, α!²⁰ ₄₃₆ +8.43°, α!²⁰₃₆₅ +8.43°(c=0.70,0.1N NaOH).

Anal-Caicd. for C₁₁ H₁₅ N₅ SO₂ : C., 46.96; H. 5.37; N, 24.90; S, 11.40.

Found: C, 46.83; H, 5.40; N, 24.88; S, 11.47.

EXAMPLE 25 (+)-(1S, 2R, 4R)-4- 2-Amino-6-(1-pyrolidinyl)-9H-purin-9-yl!-2-(hydroxymethyl)-1-cyclopentanol

(+)-(1S, 2R,4R)-4-(2-Amino-6-chloro-9H-purin-9-yl)-2-(hydroxymethyl)cydopentanol(426 mg 1.5 mmol),pyrrolidine (99%, Aldrich, 1.26 mL), and ethanol (8mL) were refluxed for 20 minutes. To the cooled solution was added 1Nsodium hydroxide (1.5 mL). Volatiles were evaporated and the residuechromatographed on silica gel. Title compound was eluted with 12%methanol-chloroform as a white solid foam which solidified from 95%ethanol to white powder (324 mg, 64%); mp 114°-117°⁻ ; mass spectrum(Cl, CH₄): 319(M+1); ¹ H-NMR (DMSO-d₆)δ: 7.81 (s, 1, H-8), 5.76 (br s,2, NH₂), 5.0-4.8 (m, 1, CHN), 4.76 (d, j=4.1 Hz, 1, OH),4.66 (t, J=5.2Hz, 1, CH₂ OH), 4.15-4.0 (m, overlapping br m at 4.1-3.4 and m at3.6-3.35, total 7, CHO, 2CH₂ N and CH₂ O), 2.4-2.2 (m, 1, 1/2CH₂),2.2-1.8 (m, 7, methylenes), 1.7-1.5 (m, 1, 1/2CH₂); α!²⁰ ₅₈₉ +10.5°,α!²⁰ ₅₇₈ +11.0°, α!²⁰ ₅₄₆ +12.4°, α!²⁰ ₄₃₆ +19.5°, α!²⁰ ₃₆₅+25.5°(c=1.43, methanol).

Anal. Calcd. for C₁₅ H₂₂ N₆ O₂ ·0.2H₂ O0.3 EtOH: C, 55.80; H, 7.26; N,25.03.

Found, C. 56.01; H, 7.31: N, 24.82.

EXAMPLE 26 (+)- (1S, 2R, 4R)-4-6-(allylthio)-2-amino-9H-purin-9-yl!-2-(hydroxymethyl)-1-cyclopentanol

(+)-(1S, 2R,4R)-4-(2-Amino-1,6-dihydro-6-thiaxo-9H-purin-9-yl)-2-(hydroxymethyl)-1-cyclopentanol (351 mg, 1.25 mmol) and 1N sodium hydroxide (1.25 mL)were stirred with allyl chloride (0.15 mL) for 5 hours. The solution wasneutralized with hydrochloric acid and volatiles evaporated. The residuewas chromatographed on silica get. Title compound was eluted with 12%methanol-chloroform as a white solid foam which solidified to whitepowder from acetonitrile (240 mg, 60% ); m.p. 133°-134°; mass spectrum(Cl, CH₄):322 (M+1); ¹ H-NMR (DMSO d₆)δ: 8.07 (s, 1, H8), 6.51 (br s, 2,NH₂), 6.10-5.85 (m, 1, CH=), 5.45-5.30 (m, 1, 1/2+CH₂ =),5.15-5.05 (m,1, 1/2CH₂), 5.0-4.8 (m, 1, CHN), 4.79 (d, J=4.1 Hz, 1, OH). 4.66 (t,J=5.2 Hz, 1, CH₂ OH), 4.15-4.0 (m, 1, CHO), 3.98 (d,J=6.9 Hz, 2, CH₂ S),3.6-3.4(m, 2, CH₂ O), 2.4-1.9 (m, 4, CH+methylenes), 1.75-1.55 (m, 1,1/2CH₂); α!²⁰ ₅₈₉ +9.30°, α!²⁰ ₅₇₈ +9.68°, α!²⁰ ₅₄₆ +11.1°, α!²⁰ ₄₃₆+18.6°, α!²⁰ ₃₆₅ +25.4°(c=0.79, methanol).

Anal. Calcd. for C₁₄ H₁₉ N₅ O₂ S: C, 52.32; H, 5.96; N, 21.79; S, 9.98.

Found: C, 25.35; H, 5.94; N, 21.82; S, 9.88.

EXAMPLE 27

(+)-(1S, 2R, 4R)-42-amino-6-(1-azetidinvl)-9H-purin-9-yl!-2-(hydroxymethyl)-1-cyclopentanol

(+)-(1S, 2R,4R)-4-(2-Amino-6-chloro-9H-purin-9-yl)-2-(hydroxymethyl)cyclopentanol(340 mg, 1.20 mmol) and azetidine (98%, ALdrich, 1.0 mL) and methanol (6mL) were maintained at 60° C. in a sealed tube for 18 hours. To thecooled solution was added 1N sodium hydroxide (1.2 mL). Volatiles wereevaporated and the residue chromatographed on silica gel. Title compoundwas eluted with methanol: ethyl acetatel 15:85 as a white foam whichsolidified to white powder from methanol-acetonitrile (333 mg, 91%), mp194°-195°; mass spectrum (Cl, CH₄) 305 (M+1)⁻ ; ¹ H-NMR (DMSO-d₆)δ: 7.81(s, 1, H8), 5.88 (br s, 2, NH₂), 495-4.80 (m. 1, CH-N), 4.76 (d, J=3.9Hz, 1, OH),4.66 (t, J=5.0 Hz, 1, CH₂ -OH). 4.4-4.15(br m, 4, 2CH₂ N),4.10-4.0 (m, 1, CHO), 3.6-3.4 (m, 2, CH₂ O), 2.5-1.9 (m, 6, methylene),1.75-1.5 (m, 1, 1/2CH₂): α!²⁰ ₅₈₉ +10.1°, α!²⁰ ₅₇₈ +10.7°, α!²⁰ ₅₄₀+11.9°, α!²⁰ ₄₃₆ +18.3°, α!²⁰ ₃₅₆ +25.2°(c=0.812, methanol).

Anal. Calcd. for C₁₄ H₂₀ N₆ O₂ : C, 55.25; H, 6.62; N. 27.62.

Found: C, 55.31; H, 6.63; N. 27.71.

EXAMPLE 28 (+)-(1S, 2R,4R)-4-(2-Amino-6-(cyclopentyloxy)-9H-purin-9-yl)-2-(hydroxymethyl)-1-cyclopentanol

Sodium hydride (60% oil dispersion, 113 mg)was added to cydopentanol(7mL). To the resulting solution, after effervescence had ceased, wasadded(+)-(1S-2R4R)-4-(2-amino-6-chloro-9H-purin-yl)-2-(hydroxymethyl)cyclopentanol(400 mg, 1.4 mmol). The solution was maintained at 8° for 40 minutes,cooled to room temperature, and neutralized with 1N hydrochloric acid.Volatiles were removed and the residue chromatographed on silica gel.Title compound was eluted with methanol: chloroform/15:85 as a whitesolid foam which solidified form acetonitrile: methanol/20:1 as a whitepowder (223 mg, 48%), m.p. 181°-182°; mass spectrum (Cl, CH₄): 334(M+1);¹ H-NMR(DMSO-d₆)δ: 7.97 (s, 1, H8), 6.32 (brs, 2, NH₂), 5.60 (m, 1, CHOof cydopentyl) 5.0-4.8 (m, 1, CHN), 4.78 (d. J=4.1 Hz, 1, OH), 4.66(t,J=5.1 Hz, 1, CH₂ OH), 4.1 (m, 1, CHOH), 3.6-3.4 (m, 2, CH₂ O),2.4-1.9 (m, 6 methylene), 1.9-1.5 (m, 7, methylene); α!²⁰ ₅₈₉ +9.34°,α!²⁰ ₅₇₈ +9.85°, α!²⁰ ₅₄₆ +11.1°, α!²⁰ ₄₃₀ +18.2°, α!²⁰ ₃₆₅ +26.6°(c=0.782, methanol).

Anal. Calcd. for C₁₆ H₂₃ N₅ O₃ : C, 57.65; H, 6.95; N, 21.01.

Found: C, 57.74; H, 6.94; N, 20.91

EXAMPLE 29 (1S,4R)-2-(2-Amino-6-chloro-4-pyrimidinyl)amino!-2-cyclopentene-1-methanol

A solution of (-)-2-azabicyclo 2.2.1!hept-5-en-3-one (Enzymatix lot#LN1253, 30.0 g, 275 mmol) in anhydrous tetrahydrofuran (150 mL) in a2L3-neck round bottom flask under nitrogen was equipped with athermometer and mechanical stirrer, then warmed to 35° C. (most of soliddissolved). Meanwhile, a solution of methanesulfonic acid (28.0 g, 291mmol) and water (5.35 g, 297 mmol) in tetrahydrofuran (50 mL) wasprepared (caution-mixing is highly exothermic). This solution was slowlyadded dropwise via an addition funnel to the 2 L flask over 10 min.Initially the solution became turbid, and by the end of the additionsome solid had appeared on the side of the flask. The mixture was heatedto gentle reflux for 3 h (internal temperature 62°-65° C.), then cooled(-15° C.). An air-dried sample of the white solid had ¹ H-NMR identicalwith the sample of (-)-(1S, 4R)-4-amino-2-cyclopentene-1-carboxylic acidmethanesulfonate described in Example 1. A solution of 1.0 N lithiumaluminum hydride in tetrahydrofuran (Aldrich, 525 mL, 525 mmol) wasadded dropwise to the mixture (slowly at first, more rapidly later) sothat pot temperature remained below 0° C. After addition was complete(required approx. 35 min) the mixture was slowly warmed to 22° C. andstirred at room temperature for 17 h, then refluxed for 5 h and cooledto ambient. Sodium fiuoride (150 g, 3.57 mol) was added, stirring wascontinued for 30 min, then the mixture was cooled on an ice bath (5°C.). Water (38 g, 2.1 mol) was added dropwise so that pot temperatureremained below 20° C. (over 30 min), then the mixture was stirred atroom temperature for 20 min and filtered. The filter cake was washedwith tetrahydrofuran/methanol (5:2), and the filtrate was set aside. Thefilter cake was taken up in tetrahydrofuran/methanol (5:2, 700 mL),stirred for 15 min, and filtered. This extraction was repeated and thethree filtrates were combined and cooled (0° C.),then refiltered. A 1 mLaliquot of this solution was concentrated to give (-)-(1S,4R)-4amino-2-cyclopentene-1-methanol as a colorless oil with identicalanalysis to the sample described in Example 2 and 3. The remainder ofthe solution was partially concentrated in vacuo, diluted with 1-butanol(500 mL), further concentrated to remove tetrahydrofuran and methanol,and transferred to a 1L3-neck flask under nitrogen equipped with athermometer and reflux condenser. Triethylamine (125 mL, 900 mmol) and2-amino-4,6-dichloropyrimidine (47.0 g, 286 mmol) were added, and themixture was refluxed for 4 h (internal temperature 107°-108° C.). Thereaction solution was partially concentrated in vacuo and treated with5N sodium hydroxide (60 mL, 300 mmol). The solution was concentrated invacuo, diluted with toluene (100 mL), and further concentrated in orderto remove the remaining triethylamine. The residual oil was taken up inchloroform (500 mL) and methanol (100 mL), then the mixture wasfiltered. The filter cake was washed with methanol/chloro-form (1:9),then the filtrate was concentrated in vacuo and the residual oildissolved in chloroform and loaded onto a column of silica gelcontaining 300 g of silica The column was initially eluted with 3%ethanol/chloroform, then with 8% ethanol/chloroform to afford purefractions of the subject compound; these were concentrated in vacuo toconstant weight to afford (1S,4R)-2-(2-amino-6-chloro-4-pyrimidinyl)amino!-2-cyclopentene-1-methanol as apale tan gum (53.1 g,75%); mp 73°-75° C. as a pale tan solid hydrate(methanol/water). ¹ H-NMR (DMSO-d₆): 7.00-7.10(br s,1H);6.35-6.45(brs,2H); 5.87(m, 1H); 5.73(s,1H); 5.71(m,1H); 4.90-5.05(br s,1H);4.64(t,1H,J=5Hz); 3.36 (m,2H); 2.6-2.75(m,1H); 2.30-2.40(m,1H);1.20-1.30(m,1H). Ms(Cl): m/z 241 (m+H+, 100). α!²⁰ ₅₈₉ -27.3° (c=0.54,methanol).

Anal. Calcd for C₁₀ H₁₃ ClN₄ O ·H₂ O: C, 46.43; H, 5.84: N, 21.66.Found: C, 46.49; H, 5.81; N, 2179.

EXAMPLE 30(1S,4R)-4-((2-Amino-6-chloro-5-((4-chlorophenyl)azo)-4-pyrimidinyl)amino!-2-cyclopentene-1-methanol

An ice cooled (5° C.) solution of 4-chloroaniline (5.74 g, 45 mmol) in amixture of water(50 mL) and concentrated hydrochloric acid (13.6 mL) wastreated dropwise with a cooled (5° C.) solution of sodium nitrite (3.11g, 45 mmol) in water (25 mL) at a rate to keep the pot temperature below10° C. This solution was placed in a dropping funnel and added dropuwiseto a mechanically stirred cooled (5° C.) solution of sodium acetatetrihydrate (49 g, 360 mmol) and(1S,4R)-(2-(2-amino-6chloro-4-pyrimidinyl)amino)-2-cyclopentene-1-methanolhydrate (9.99 g, 40 mmol) in water/acetic acid (1:1, 100 mL) at a rateto keep the pot temperature below 10° C. The mixture was warmed andstirred at room temperature for 18 h, then filtered. The filter cake waswashed with water, air dried, and triturated from acetonitrile to afford14.26 g (91%) of the title compound as a hydrate (1:0.75); mp 218°-20°C. (dec). ¹ H NMR(DMSO-d₆): 10.25(d,1H,J=7Hz); 7.70(d,2H,J=9Hz);7.55(d,2H,J=9Hz); 594(m,1H); 5.83(m,1H); 5.20-5.30(m,1H);3.35-3.50(m,2H); 270-2.80(m,1H); 2.40-2.50(m,1H); 1.40-1.55 (m,1H). Ms(Cl): m/z 283 (m-C5 ring, 60); 343 (m-Cl, 40); 379 (m+H⁺, 100). α!²⁰ ₅₈₉+26.8° (c=0.51, methanol).

Anal. Calcd for C₁₆ H₁₆ Cl₂ N₆ O·0.75H₂ O: C, 48.93; H, 4.49; N, 21.40.Found: C, 49.02; H, 4 51; N, 21.42.

EXAMPLE 31 (1S,4R)-(4-(2,5-Diamino-6-chloro-4-pyrimidinyl)amino)-2-cyclopenten-1-methanol

A suspension of(1S,4R)-4-((2-amino-6-chloro-5-((4-chlorophenyl)azo)-4-pyrimidinyl)-amino)-2-cyclopentene-1-methanolhydrate (0.76g, 2.0 mmol) in methanol/acetic acid/water (6:2:1, 9 mL)was treated in portions over 10 min with zinc powder (1.0 g, 15.3 mmol)so that the pot temperature remained below 35° C. The mixture wasstirred at room temperature for 1 h and at 40° C. for 1 h, thenconcentrated in vacuo with addition of toluene to remove acetic acid andwater. The residue was taken up in 5% isopropanol-chloroform and loadedonto a silica gel column, which was eluted with 8%isopropanol-chloroform, then with 15% isopropanol-chloroform to affordpure fractions of the subject compound, which were combined andconcentrated in vacuo to afford(1S,4R)-(4-(2,5-diamino-6-chloro-4-pyrimidinyl)amino)-2-cyclopenten-1-methanol as a pink-tan solid (0.39 g ,76%); mp 159.5°-161.0° C. ¹ HNMR (DMSO-d₆): 6.41(d, 1H, J=7 Hz); 5.85-5.95(m,1H); 5.70-5.80(m,1 H);5.62(br s,2H ); 5.00-5. 15(m,1 H); 4.67(t,1H, J=5 Hz); 3.96(br s,2H);3.35-3.45 m,2H); 2.60-2.80(m, 1H); 2.30-2.50(m,1H); 1.20-1.40(m, 1H). Ms(Cl): m/z 160 (m-C5 ring, 90); 220 (m-Cl, 40); 255 (m+H+, 100). α!²⁰ ₅₈₉+0.37°, α!²⁰ ₄₃₆ -9.41°(c=0.54, methanol).

Anal. Calcd for C₁₀ H₁₄ ClN₅ O: C, 46.97; H, 5.52; N, 27.39. Found: C,47.03; H, 5.54; N, 27.45.

EXAMPLE 32 (1S,4R)-4-(2-Amino-6-chloro-9H-purin-9- yl)-2-cyclopentene-1-methanol

A suspension of (1S,4R)-4-((2-Amino-6-chloro-5-((4chlorophenyl)azo)-4-pyrimidinyl)amino)-2-cyclopentene-1-methanolhydrate (1.96 g, 5 mmol) in tetrahydrofuran (15 mL) was treated withacetic acid/water (1:1, 5 mL), then with zinc dust (1.63g, 25 mmol) inportions so as to keep the pot temperature below 35° C. The deep yellowcolor faded after 10 min, and after an additional 50 min the solutionwas filtered to remove precipitated zinc salts. The filter cake wasrinsed with tetrahydrofuran and the filtrate was refiltered to removeadditional zinc salts, then concentrated in vacuo with addition oftoluene to facilitate removal of water and acetic acid. The residue wasrinsed with toluene/hexane to separate some of the 4-chloroanilinebyproduct, taken up in triethyl orthoformate (40 mL), cooled on an icebath (5° C.), and treated dropwise with concentrated hydrochloric acid(1.9 mL). The mixture was stirred at 5° C. for 5 h (tan suspension soonformed), slowly warmed to room temperature, and stirred for anadditional 18 h, then cooled on an ice bath and filtered. The filtercake was rinsed with ether (save filtrate), and this solid was taken upin water (30 mL), filtered, and the solids washed with water. Theaqueous filtrate was basified with sodium carbonate to pH-9, thenextracted with 5% isopropanol-hloroform (3×25 mL) The combined extractswere dried (Na₂ SO₄) and concentrated in vacuo to a residual tan foam(0.85 g). The organic filtrate from above was concentrated in vacuo andthe residue taken up in 1N hydrochloric acid (30 mL), stirred for 1h,filtered, and the filtrate adjusted to pH-6 with 5 N sodium hydroxide (6mL, then basified with sodium carbonate. This aqueous suspension wasextracted with 5% isopropanol-chloroform (3×25 mL), and the combinedorganic extracts were dried (Na₂ SO₄) and concentrated in vacuo to a tanfoam (0.55 g ). The two batches were combined, dissolved in warmchloroform, and loaded onto a silica gel column, which was eluted with7% methanol-chloroform to afford pure fractions containing the subjectcompounds. These were concentrated in vacuo and the residual foamcrystallized from ethyl acetate(2 crops) to afford 0.86 g (65%) of thetitle compound as a pale tan solid; mp 160°-162° C. ¹ H-NMR (DMSO-d₆)δ:8.04(s,1H); 6.91(s,2H); 6.15(m,1H); 5.90 (m,1H); 5.45 (m,1H); 4.73 (t,1H,J =5 Hz); 3.45 (t,2H,J=5 Hz); 2.80-2.95(m, 1H); 2.55-2.70(m,1H);1.60-1.70(m,1H). Ms(Cl): m/z 170 (m-C5ring, 100); 230 (m-Cl, 50); 266(m+H+, 100). α!²⁰ ₅₈₉ -104°, α!²⁰ ₄₃₆ -267°(c=0.29, methanol).

Anal. Calcd for C₁₁ H₁₂ ClN₅ O: C, 49.73; H, 4.55; N, 26.36. Found: C,49.89; H, 4.61; N, 26.25.

EXAMPLE 33 (-)-(1S, 4R)-4-2-Amino-6-(cyclopropylmethylamino)-9H-purin-9-yl!-2-cyclopentene-1-methanol

(1S, 4R(2-amino-6-chloro-9H-purin-9-yl)-2-cyclpentene-1-methanol (274mg, 1.00 mmol), N-cydopropyl-N-methylamine (0.71 g, 10 mmol) andabsolute ethanol were refluxed for 5.0 hpurs. Volatiles were evaporatedand the residue chromatograped on silica gel. Title compound was elutedwith 10% methanol-chloroform as a colorless glass. Evaporation of anethanol solution gave title compound as a colorless solid foam (293 mg,98%). ¹ H-NMR (DMSO-d₆) δ: 0.56 and 0.63 (2m, 4, 2-cydopropyl CH₂), 1.56and 2.60 (2m, 2, cyclopentenyl CH₂), 2.85 (m, 1, H-4'), 3.02 (m, 1,cyclopropyl CHNH), 3.43 (m, 2, CH₂ OH), 4.71 (t, 1, CH₂ OH); 5.40 (m, 1,H-1'), 5.85-5,70 (m overlapping s at 5.77, 3, N H₂ and =CH), 6.09 (m, 1,=CH), 7.23 (d, 1, NHCH), 7.58 (s, 1, purine H-8); ms (Cl) 287 (m+1).α!²⁰ ₅₈₉ -59.7°, α!²⁰ ₄₃₆ -128°(c=0.15, methanol).

Anal. Calcd. for C₁₄ H₁₈ N₆ O·0.15 EtOH·0.05 H₂ O: C, 58.39: H, 6.51: N,28.57. Found: C, 58.11: H, 6.84; N, 28.92.

EXAMPLE 34

(+)-(1R, 4S)-4-Amino-2-cyclopentene-1-methanol

A mixture of (-)-(1S, 4R)4amino-2-cyclopentene-1-carboxylic acid (ChirosLtd., Cambridge, England; 40.00 g, 0.315 mole) in dry tetrahydrofuran(300 mL) was stirred in an ice bath while 1 M lithium aluminum hydridein tetrahydroturan (Aldrich, 485 mL) was added over 1.5 hours. Thetemperature during this addition was not allowed to exceed 0° C. Themixture was brought to ambient temperature and then to reflux over onehour and maintained at reflux for 2.5 hours. The mixture was allowed tocool to ambient temperature and sodium fluoride (89.6 g) was added andstirring continued for an additional 0.5 hour. The mixture was cooled(ice bath) and water (23 mL) added slowly. Stirring was continued for anadditional 0.5 hour. The precipitate was filtered and extracted with 40%methanol-tetrahydrofuran (2×300 mL). The filtrate-wash was concentratedin vacuo to a colorless oil which darkened rapidly in air and light.Such a sample was dried at ambient temperature/ 0.2 mm Hg to a paleyellow oil; ¹ H-NMR(DMSO-d₆) identical to that of the enantiomerdescribed in Example 1, d: 5.67 (m, 2, CH=CH), 3.8-3.7 (m, 1, CHN), 3.32(d, J=6.0 Hz, overlapped by broad D₂ O-exchangeable peak centered at3.18, CH₂ O, OH, NH₂ and H₂ O in solvent), 2.68-2.56 (m, 1, H-1),2.28-2.18 (m, 1, 1/2CH₂), 1.08-0.98 (m, 1, 1/2CH₂); mass spectrum(Cl):114(M+1); α!²⁰ ₅₈₉ 55.0°, α!²⁰ ₅₇₈ +58.3°, α!.sup.°₅₄₆ +67.4°, α!²⁰ ₄₃₆+119° (c=0.242, methanol).

Anal. Calcd. for C₆ H₁₁ NO·0.31 H₂ O: C, 60.69; H, 9.86; N, 11.80.Found: 61.12;H, 9.79; N, 11.38.

We claim:
 1. A process for the preparation of a compound of formula(VIIIb), wherein X represents an anion, its mirror ##STR11## imageenantiomer or a mixture of such enantiomers which comprises reacting(-)-2-azabicyclo 2.2.1!hept-5-ene-3-one of formula (IX), its mirrorimage enantiomer or a mixture of such enantiomers ##STR12## with one ormore equivalents of an acid and one or more equivalents of water.
 2. Aprocess as claimed in claim 1 wherein the said acid has a pKa of lessthan two.